Azure Notification Hub: Test Send returning unknown error on browser push, although info is passed correctly with tags

Question

Azure Notification Hub: Test Send returning unknown error on browser push, although info is passed correctly with tags

Agarwal, Ansh 50

We are experiencing failure when test sending notification to browser

Test Send returning unknown error on browser push, although info is correctly passed, and we also have on our side browser registered with tag which is passed. (check screenshots)

kindly guide what is error which is said as unknown by notification hub? Just to inform, our browsers are continuously listening for the notification to come, but they are not reaching there.

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Prabhavathi Manchala 2,315 Reputation points Microsoft External Staff Moderator

2025-06-17T09:37:11.0633333+00:00
Hi Agarwal, Ansh,

You're seeing an unknown error when sending test notifications to browsers via Azure Notification Hubs. This often happens due to a few common issues:

Missing or incorrect web push certificates (VAPID keys)

Expired or invalid browser registration tokens

Tag expressions not matching any registered devices

Improper service worker setup on the browser side

CORS or domain-related restrictions blocking the notification

1). Verify Web Push Configuration

First, ensure your Azure Notification Hub is properly configured for web push:

Check VAPID Keys: Navigate to your Notification Hub → Settings → Web Push Settings and ensure that valid VAPID keys are configured. If you're using FCM, also verify that your FCM sender ID and server key are correct.

Verify Certificate Validity: If using certificates instead of VAPID keys, ensure they haven't expired.

2). Validate Browser Registration

Make sure your browser clients are registered and have valid tokens. Try forcing them to re-register to get fresh tokens. Also, check that the collections_chrome tag is correctly assigned during registration.

3). Ensure the browser's service worker is correctly configured and functioning properly.

4). Test with Direct Registration

Test by sending a notification directly to a browser's registration token—if it works, the problem is likely with the tag expression.

5). Verify Payload Format

Ensure your notification payload is correctly formatted for web push:

{ "title": "Test Notification", "body": "Notification Hub test notification", "icon": "/icon.png", "badge": "/badge.png", "data": { "url": "https://your-website.com" } }

6). Enable Diagnostic Logging

Turn on detailed logging in Azure Notification Hubs by going to Monitoring → Diagnostic Settings and enabling OperationalLogs and DebugLogs to help find the cause of the unknown error.

Web push notifications with Azure Notification Hubs

Push Notification Fixer Guide

Push Notification Registration Management
Agarwal, Ansh 50 Reputation points

2025-06-17T09:46:37.0566667+00:00

@Prabhavathi Manchala we are already followed above provided steps it is giving unknown error, there is no issue of payload, or any of what you descirbed.

But, one thing i can see from metrices the notification hub i guess not able to send the notification to PNS, because i can see errors under external notification system error category (As in below screenshot). Kindly guide on this

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Agarwal, Ansh 50 Reputation points

2025-06-17T09:46:37.0566667+00:00

@Prabhavathi Manchala we are already followed above provided steps it is giving unknown error, there is no issue of payload, or any of what you descirbed.

But, one thing i can see from metrices the notification hub i guess not able to send the notification to PNS, because i can see errors under external notification system error category (As in below screenshot). Kindly guide on this

Answer 1

Alex Burlachenko 9,780

hi ansh ))

thanks for posting this q on the q&a, its super helpful when folks share details like screenshots, really thx.

So, check if u registered the browser platform correctly in azure. sometimes the p12 certificate or vapid keys get messed up during setup. also peek at the hub's diagnostic logs - they often hide clues that the ui doesn't show.

and try sending without tags first. just hit 1-2 test devices directly. if that works, then bam - tag expressions might be the sneaky culprit.

make sure ur service worker is awake and kicking. browsers love to put them to sleep like lazy cats. u can test this in chrome devtools under 'application > service workers'.

also worth trying a different payload sizes. sometimes that 'unknown error' is just hub being picky about message length. start small then grow.

and this might help in other tools too, check ur CORS settings. browser pushes get real fussy about cross origin stuff. devtools console will yell at u if thats the issue.

keep us posted if these dont work %)

rgds,

Alex

Agarwal, Ansh 50 Reputation points

2025-06-17T10:07:33.3666667+00:00

Hi Alex Burlachenko, browser platform is registered correctly, without tags also we are getting same error, service worker is also awake.
From the screenshot I provided it seems notification hub is not able to reach to PNS. But I don't understand about the CORS where to check this.
Alex Burlachenko 9,780 Reputation points

2025-06-17T10:22:11.74+00:00

hey hey,,, registration's good, service worker's awake, tags ain't the issue. time to hunt deeper ))

for the PNS reachability problem u spotted in screenshots - let's check these chrome specific stuff first.... u using vapid keys? sometimes they expire or get misconfigured.

peek at chrome's developer console (F12 > console tab) while sending. if u see cors errors there, that's what we are looking for ))

try testing on http://localhost if u're on https. chrome blocks some push stuff on insecure origins where cors gets sneaky? cors errors usually pop up in browser's dev console (F12 > console) check ur notification hub's allowed origins under CORS settings in azure portal, make sure ur website's domain matches exactly what's registered...

chrome gives specific cors error messages like "blocked by cors policy" - those help a ton.

try that one if other non helps, create an fresh test hub with minimal config, register just one test device, send simplest possible payload {"title":"test"}..

if this fails, might be account-level issue...

different browser altogether like firefox. their error messages are sometimes clearer than chrome's %)

rgds,

Alex
Agarwal, Ansh 50 Reputation points

2025-06-17T10:53:51.69+00:00

Hi Alex Burlachenko, I am actually not yet on https, actually testing on localhost iteself, and tried on both edge and chrome, and in console there is no error of CORS. and also one more thing interestingly if I attempt to push directly to PNS from python like using pywebpush directly using subscription endpoint,auth and key (directly means -- not via noti hub but directly to PNS from pywebpush) i am getting notification browser, but it is through notification hub i am facing issue.
Alex Burlachenko 9,780 Reputation points

2025-06-17T12:27:36.03+00:00
Hi, since localhost/http works fine with direct pushes, we can rule out browser level issues. this is 100% about how notification hub talks to PNS. check vapid keys configuration, u might have set different vapid keys in notification hub vs what pywebpush uses. go to azure portal > notification hub > chrome configuration. compare those vapid keys with what's in ur python code.

payload format differences, notification hub might be modifying the payload structure, try sending this bare minimum payload through hub

{"notification":{"title":"test","body":"test"}}

sometimes hub adds extra wrappers that chrome doesn't like.

timeout settings, notification hub has default 30s timeout to PNS.., try increasing it to 60s in hub settings, localhost might respond slower than azure expects ))

certificate weirdness, even though u're on http, hub still needs valid ssl certs, check azure activity logs for any certificate errors

try to enable verbose logging in notification hub. the 'unknown error' often hides more details in the backend logs. go to diagnostic settings and turn everything to 'verbose' ))

also interesting - since edge fails too, its definitely not chrome-specific. makes me think its either vapid key mismatch (most likely), payload formatting issue, azure-side config hiccup. Try regenerating vapid keys completely and updating both python and azure. sometimes that magically fixes things %)

keep me posted! this is getting interesting )

Alex
Agarwal, Ansh 50 Reputation points

2025-06-17T17:31:07.3266667+00:00

Hi Alex Burlachenko, I have checked 1. vapid keys --> these we are mentioning correct, 2. checked the step you suggested of sending the payload, still it is failing, below is the screenshot
Prabhavathi Manchala 2,315 Reputation points Microsoft External Staff Moderator

2025-06-18T11:15:56.39+00:00
Hi Agarwal, Ansh,

From your screenshot, you've used the correct payload {"notification":{"title":"test","body":"test"}}, but the "unknown error" still appears. Since pywebpush works fine, the issue likely lies in a mismatch between your Azure Notification Hub settings and the browser's push subscription.

The most likely issue is a mismatch between the VAPID keys in your JavaScript and those in Azure Notification Hub. Another possible cause is an invalid browser push token format that Azure can’t process. There might also be a misconfiguration in the Chrome setup within the Notification Hub.

Please follow the below steps to resolve this issue:

Step 1: Verify VAPID Key Consistency

Make sure the applicationServerKey in your JavaScript matches the VAPID key set in Azure Notification Hub.
navigator.serviceWorker.ready.then(registration => { return registration.pushManager.subscribe({ userVisibleOnly: true, applicationServerKey: urlBase64ToUint8Array('YOUR_VAPID_PUBLIC_KEY') }); });

Compare with the Azure Portal, under Notification Hub → Settings → Google (GCM/FCM), ensure the public and private VAPID keys exactly match those used in your JavaScript.

Web push notifications with Azure Notification Hubs

Step 2: Check Registration Format

Retrieve the browser's subscription object in your JavaScript code.
navigator.serviceWorker.ready.then(registration => { return registration.pushManager.getSubscription(); }).then(subscription => { console.log('Full subscription object:', JSON.stringify(subscription, null, 2)); });

Verify the registration format in Azure Notification Hub by ensuring it includes endpoint, keys.p256dh, and keys.auth, all correctly stored.

Push notification registration management

Step 3: Enable Detailed Logging

Turn on diagnostic logging in Azure Portal by enabling OperationalLogs and RuntimeAuditLogs under Notification Hub → Monitoring → Diagnostic Settings, and set the log level to Verbose.

Check the logs after sending a test notification to see the exact error details.

Notification hubs diagnostic logs
Alex Burlachenko 9,780 Reputation points

2025-06-18T13:47:38+00:00

Agarwal, Ansh hi, had u chance to revie my answer?

rgds,

Alex
Agarwal, Ansh 50 Reputation points

2025-06-18T16:18:50.55+00:00

hi @Alex Burlachenko i have reviewed your answer, and also commented can you check my last comment provided with screenshot of test send?
Prabhavathi Manchala 2,315 Reputation points Microsoft External Staff Moderator

2025-06-19T10:03:38.3066667+00:00

Hi Agarwal, Ansh,

I have checked your last comment with the screenshot and replied based on the details you shared. Kindly check my last response for the update. Let me know if you have any further questions.
Agarwal, Ansh 50 Reputation points

2025-06-20T12:15:38.91+00:00

Hi @Prabhavathi Manchala I have tried all the things, triple checked everything is correct from browser side and from installation side, only thing is it is not able send it from notification hub to PNS as i shared in above screenshot, in metrices it showed as notification external system error, Now only thing I left with is to enable the logs that will take bit of time for me to enable them, as this is not currently approved. But if feel any other suggestion then surely i could try

thanks
Prabhavathi Manchala 2,315 Reputation points Microsoft External Staff Moderator

2025-06-20T14:19:43.36+00:00
Hi Agarwal, Ansh,

Apologies for the inconvenience, while you're waiting for log access, please check the Azure Activity Log, it doesn’t need any special permissions and can help identify the issue.

Go to Azure Portal → Activity Log

Filter by your Notification Hub resource name

Look for failed operations in the last 24 hours

Check for any certificate, authentication, or quota-related errors

Azure Activity Log Analysis

The portal often shows a vague "unknown error," but using the REST API provides detailed HTTP status codes and error messages, making it easier to identify the exact issue.

POST https://[hub-name].servicebus.windows.net/[hub-name]/messages/?api-version=2015-01 Authorization: SharedAccessSignature [your-connection-string] Content-Type: application/json ServiceBusNotification-Format: browser {"title":"REST API Test","body":"Direct API call"}

Notification hubs direct send

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Azure Notification Hub: Test Send returning unknown error on browser push, although info is passed correctly with tags

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