[BUG] Calling into Custom Android Client gets forwarded to VoiceMail

[Taving40]

Describe the bug
We're experiencing a big issue with listening to incoming calls on our devices - it stopped working completely using your Android SDK library: callAgent.addOnIncomingCallListener()

We didn't release any new version recently, and outgoing calls proceed to work, but incoming ones aren't even registered anymore. The user calling our device gets forwarded to VoiceMail immediately.

Exception or Stack Trace
In the following files you can see:

• acs_sdk-*.blog - blog files associated with the issue:
• teams_1.log & full_issue_1.log - starting with 06-18 13:26; app package name com.realwear.acs was waiting for incoming call with CallId ff3c03e8-ce17-4719-bef2-9c9a6bcfb8dd from MS Teams official desktop client for Mac. Instead of being received it was forwarded to VoiceMail.

Additionally, below I have extracted some logs from admins.teams.microsoft.com for the associated CallId

Report time
Jun 18, 2025 at 1:27 PM GMT+3
Cnd_Skype_ResultDetail
Received 404 Not Found from Trouter client when trying to send Http message via Trouter.
Cnd_Skype_InitiatingUser_Endpoint_EndpointValue
55b7a022-7f90-8a6c-0050-cfbd4c920893
Cnd_ClientHeader
True
Cnd_Skype_ResultCode
404

To Reproduce
This has a repro-rate of 4/7 using only the Desktop Client as the call initiator. To reproduce we only need to call from the Desktop Client into the custom app repeatedly and it will sometimes forward the user to VoiceMail.

We are happy to schedule a meeting with one of our devs to reproduce this in a controlled environment.

Code Snippet
callAgent.addOnIncomingCallListener()

Expected behavior
The call should go through and be received on the app side.

Screenshots
N/A

Setup (please complete the following information):

• OS: AOSP based (Android 13)
• IDE : N/A
• Version of the Library used:
  • azure-communication-calling - 2.12.0
  • azure-communication-identity - 1.6.1
  • com.microsoft.identity.client - 5.8.3

Additional context
N/A

Information Checklist
Kindly make sure that you have added all the following information above and checkoff the required fields otherwise we will treat the issuer as an incomplete report

• Bug Description Added
• Repro Steps Added
• Setup information Added

[jamchengms]

Hi @Taving40,

Thanks for sharing the call id and the blog files.

We looked at your scenario and have confirmed that the realwear device (which utilizes ACS Calling SDK) did not receive the incoming call. To better assist you, we'd like to gather some information about your setup.

1. Are you utilizing FCM for push notification? If yes, are you aware that FCM registrations for Microsoft Teams User is 24 hours only. See https://learn.microsoft.com/en-us/azure/communication-services/how-tos/calling-sdk/push-notifications?pivots=platform-android#-overview-of-ttl-tokens for reference.
2. Is the realwear application in foreground or background or phone locked when you are trying to receive the notification?
3. Are there multiple clients logged in as the Microsoft Teams User in other devices?
4. Does the call go to voicemail right away or does it ring for a few seconds before getting redirected to voicemal?

In terms of debuggability, I would recommend you start with a fresh install, reproducing the problem and send us all the blog files that has been collected from the realwear devices. Reason being, the blog files you've shared don't contain the CallId ff3c03e8-ce17-4719-bef2-9c9a6bcfb8dd in it. Also, please do also share with us CallId and blog files for the scenarios that you are getting a push notification. We can cross reference with cases that worked vs not working.

[oleksandr-hulak]

Hi @jamchengms, I work with @Taving40 on the same project.

Answering your questions:

1. No, we don't use FCM as it requires Google Play Services, which don't run on our custom AOSP. For the moment, we rely on your addOnIncomingCallListener, when the app is in foreground. We will probably later add a foreground service.
2. The app is in foreground, the phone is unlocked.
3. We checked those scenarios - the issue happens even if the Teams user is logged in on a single device.
4. It rings for a second, and then gets forwarded to voicemail. The receiving side doesn't get that incoming call. What's odd is that it was previously working for us in like 70-75% of sessions. Now it doesn't seem to work at all.

We did a fresh install, single sign in, here are the logs for the 3a9d064a-37ea-4814-8ca9-344daba635fd call session, together with the call report:
https://realwear-my.sharepoint.com/:f:/p/oleksandr_hulak/EoDjEzvgSN1InNaNJvz0yCYBe_2YwWWHzywhcj6pSHOUFg?e=sVFO9s

What I find odd is the call receiver info - the OS is "Windows", though our client runs on a custom Android OS.

[jamchengms]

We've noticed in our server side logs that once the call is received, it's automatically being forwarded to voicemail (within 30 milliseconds) which indicates to us that in teams admin center you have voicemail configuration changes for this particular user.

Can you check the Settings -> Calls -> Configure Voicemail in teams admin center and let us know what value you have set for this user? For reference: https://learn.microsoft.com/en-us/microsoftteams/manage-voicemail-settings

[oleksandr-hulak]

@jamchengms, these are the user's voicemail config. I'm not so sure if it's related to the bug, because it's reproducible across multiple tenants, different users, and the call goes through if the user is logged in on a Teams Desktop client.

[oleksandr-hulak]

Hi @jamchengms, do you have any updates?

[oleksandr-hulak]

Hi @jamchengms @lisaleehan, when can we expect to hear from you?

[raosanat]

@oleksandr-hulak this seems to be a similar issue that we have been chasing, looks like Registration request has been failing which is causing the incoming call to not be receieved and then it get forwarded to voicemail. It seems to be some issue with Certificates installed on the device.
We will get back with more details.

[oleksandr-hulak]

@raosanat thank you, looking forward!

[oleksandr-hulak]

Hello @raosanat, it has been a while since the last update. Do you have any progress on this?

[Ivan3ol]

@oleksandr-hulak Have you resolved this issue in any way? Having the same one

[oleksandr-hulak]

@oleksandr-hulak Have you resolved this issue in any way? Having the same one

That was indeed something on the cloud side, because the issue got solved after Microsoft replied. We still saw it a couple of times after a few months, but it was not affecting us that much.