Skype for business 2019 Android issue

Rust 1

Hello, colleagues. I have a skype for business 2019 deployment. 1 Standart front end server , 1 edge server and 1 reverse Proxy on iis arr. A few days ago, all logon attempts from android devices stopped working. I can sign in from ios devices, but can't sign in with all android devices. In client logs I can see Post query to web ticket service. On the next step I'm getting 502 error. In ios client log, webticket service returns code 200 and then client goes to autidiscover service. Any ideas? Thanks.

JimmyYang-MSFT 53,851 Reputation points Microsoft Vendor

2023-04-19T07:42:45.8966667+00:00
@Rust
Are there any error messages when sign in Skype for Business for Android? What is your internet connection way? WiFI or 4G? To troubleshoot, use one or more of the following methods, as appropriate for your situation:

Use the nslookup command and a public DNS server to determine whether the DNS CNAME record is configured correctly.

If the user has the option, have the user switch between Wi-Fi and 3G to determine whether the issue can be scoped to one kind of connection. If sign in continues to fail on a 3G data connection, although the CNAME DNS records are configured, it may be an issue with the cellular service provider's data connection.
Rust 1 Reputation point

2023-04-19T10:03:35.97+00:00
Yes, i see the following error: "Unable to connect to server. If you are using a wi-fi connection, open a browser and check if there is a connection...". I've tried both connection types with no success. Dns records are fine, because IOS devices can successfully connect. As i understood, the sign-in process goes like this:

SFB client Queries DNS for Lyncdiscover.domain.com. This should point to Webdir.domain.com

SFB Client then sends a unauthenticated GET request to Lyncdiscover.domain.com

The Client is then redirected to Autodiscover service webext.domain.com/Autodiscover/AutodiscoverService.svc/root/user

SFB Client then sends a Request to Autodiscover to discover its pool for sign in.

The Client is then challenged and is provided the URL for Webticket service webext.domain.com/WebTicket/WebTicketService.svc/mex and must get status code 200

The Client sends POST to webext.domain.com/WebTicket/WebTicketService.svc and must get status code 200, but i receive status code 502 (Web server received an invalid response while acting as a gateway or proxy server. There is a problem with the page you are looking for, and it cannot be displayed. When the Web server (while acting as a gateway or proxy) contacted the upstream content server, it received an invalid response from the content server. IOS device at 6 step receives status code 200 and goes to the next step with the same sfb account. So, the problem is somewhere here. By the way, i can connect from my mobile device to another similar installation, to exclude problems with my device or app.
JimmyYang-MSFT 53,851 Reputation points Microsoft Vendor

2023-04-26T07:51:52.6766667+00:00

@Rust We will check it later.

1 answer

Rust 1 Reputation point

2023-06-02T19:39:56.7566667+00:00

Hello colleagues. I was able to remember what problem could lead to this behavior.

Some time ago (about a month before the problem with mobile login was discovered) on the reverse proxy server (Windows server 2019+IIS ARR) the Default application pool stopped running.

The error was of the form: "A listener channel for protocol 'http' in worker process '#' serving application pool 'DefaultAppPool' reported a listener channel failure. The data field contains the error number." Event ID 5139, WAS

Some time later I accidentally discovered that if I change the Identity of the App pool from "ApplicationPoolIdentity" to Local system, the pool stops crashing and works. At this point, I calmed down, but the root cause of this behavior was this. I eventually failed to get the pool to start under Identity "ApplicationPoolIdentity", so I simply re-deployed the server and reconfigured it.

It is important that the DefaultApplicationPool should work with Identity "ApplicationPoolIdentity".

Right now, everything works fine -my problem was solved.

Maybe my answer will help someone with the same problem and save a lot of time.
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Skype for business 2019 Android issue

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