Microsoft Foundry AI Agents won't respond - 404 errors in browser console.

Question

I'm trying to create and test some agents in the new Foundry portal. When I send a message from within the creation window, I get no response, and there is a 404-error message relating to Microsoft's servers. This was working for me yesterday and I changed nothing. I have tried creating new agents from scratch, changing the model, re-authenticating, etc.

Answer 1

Hello Nick Burke,

Welcome to Microsoft Q&A and Thank you for reaching out.

From your console error:

POST https://ai.azure.com/nextgen/api/query/createAgentConversationResolver 404 (Not Found)
AxiosError: ERR_BAD_REQUEST

This is failing on a NextGen portal backend route, not on your model deployment.

Things to Check

1.Please Check Azure Service Health

Go to Azure Portal → Service Health Look for issues affecting:

Azure AI Foundry

Azure AI Services

• Your specific region
• Azure Service Status

Sometimes partial control-plane outages don’t immediately show up in the portal UI.

2.Clear Cache / Session State

Since this is a portal call:

Sign out of Azure completely

Close the browser

Reopen in InPrivate/Incognito

Log back in fresh

This rules out stale auth tokens or cached frontend bundles.

3.Try a Different Browser

Sometimes cached JavaScript bundles cause the UI to call outdated endpoints. Trying Chrome/Edge/Firefox fresh can eliminate that.

4.Verify Network / Firewall

If you're on a corporate network:

Ensure nothing is blocking ai.azure.com

Confirm no proxy or firewall is interfering with API calls

However, since you're getting a 404 (not blocked/timeout), this is less likely.

5.Authentication Token Expiry

Even though you re-authenticated, sometimes:

Session token expires

Agent runtime token fails silently

Full logout + private window usually resolves that if it’s the cause.

Why This Still Looks Service-Side

The failing endpoint:

/nextgen/api/query/createAgentConversationResolver

is part of the NextGen Foundry control plane, not the model inference endpoint.

A 404 on that route means:

Backend route not deployed

Feature flag mismatch

Regional control-plane issue

• Partial rollout regression

Since it worked yesterday, the most probable cause is a backend deployment change.

Workarounds

Use Classic Foundry

If Classic works, you can continue testing there.

Call the Agent via SDK / REST

If direct API calls succeed, the issue is limited to the portal UI.

I Hope this helps. Do let me know if you have any further queries.

Thank you!