**3CX V20 Update 10 – Microsoft 365 users not linked to existing extensions, missing Teams mapping, SIP 603 Decline**

[appservices@bergmanbrothe]

Hello 3CX Team,

We are experiencing a Microsoft 365 / Microsoft Teams Direct Routing integration issue with 3CX V20 Update 10, running on an Ubuntu Linux server hosted in Microsoft Azure.

Our Microsoft Teams Direct Routing integration is operational for most users. However, four existing 3CX users are not being properly associated with their Microsoft 365 identities.

Symptoms:

1. The affected users do not display the green Microsoft 365 synchronization icon in the 3CX Users administration interface.
2. At least three affected users are missing from the Teams map_users.ps1 script generated by 3CX.
3. Outbound calls from Microsoft Teams fail immediately with SIP 603 Decline, Microsoft diagnostic subcode 560603.
4. Other users can successfully make calls through the same SBC and Direct Routing configuration.
5. Incoming calls to at least one affected user are routed to the 3CX application rather than Microsoft Teams.

What we have already verified:

• All affected users belong to the Microsoft 365 group, which is selected for synchronization in 3CX.
• Microsoft 365 user synchronization and Teams integration are enabled.
• Microsoft Graph application permissions, including User.Read.All and Group.Read.All, have administrator consent.
• UserPrincipalName, Mail, and Primary SMTP addresses match for the user investigated in detail.
• Microsoft Teams users have Enterprise Voice enabled.
• Direct Routing phone numbers and extensions are assigned correctly.
• Teams voice routing policies and dial plans are configured.
• The SBC TLS certificate, SIP TLS port 5061, and connectivity have been validated.
• Other users work correctly through the same infrastructure.

Additional findings:

Historical 3CX logs contain a Microsoft 365 synchronization error involving UserSync.SynchronizeUserCoreAsync and Commit failed on transaction Save Wextension, although that specific error references another extension.

We also found Microsoft Graph email errors for one affected user, but Exchange Online confirms that the account has a UserMailbox. We have not established that these email errors are related to the Teams mapping problem.

Our main concern:

It appears that 3CX is not associating certain Microsoft 365 identities with their existing PBX extensions. Consequently, those users are excluded from the generated Teams mapping script.

We need to restore these associations without deleting or recreating the existing extensions, since some belong to company owners and contain important production configurations.

Questions for 3CX Support:

1. Is there a supported way to force Microsoft 365 user synchronization or re-associate an existing 3CX extension with its Microsoft Entra ID identity?
2. Can an incorrect or stale Microsoft 365 user mapping prevent an extension from appearing in map_users.ps1?
3. Which logs or diagnostic tools can identify why a particular Microsoft 365 user is excluded from Teams mapping?
4. Is there a supported recovery procedure that preserves existing extensions, call history, and configuration?

We would appreciate guidance on resolving this urgently, as the affected users cannot use Microsoft Teams calling.

Thank you.

 

[Claas Felix Beyersdorf]

What do you mean with the 3CX ist running on an Ubuntu?
Is this your Hypervisor Host, Hosting the required Debian 12 VM for 3CX?
As everything else wouldn't be supported and the 3CX support wont help you at all.

I've seen sometimes problems if you haven't enabled the "Sync User Informations" part as 3CX Syncs AZURE_UPNs.. wich will never be updated afterwards (as normally no one would change them in M365). But if this Azure UPN is not in sync with M365 it is like an local only user.

 

[appservices@bergmanbrothe]

What do you mean with the 3CX ist running on an Ubuntu?
Is this your Hypervisor Host, Hosting the required Debian 12 VM for 3CX?
As everything else wouldn't be supported and the 3CX support wont help you at all.

I've seen sometimes problems if you haven't enabled the "Sync User Informations" part as 3CX Syncs AZURE_UPNs.. wich will never be updated afterwards (as normally no one would change them in M365). But if this Azure UPN is not in sync with M365 it is like an local only user.

Hi Felix, I have my 3CX hosted on Azure. Actually, we have the rest of the users calling through Teams, and I have investigated the issue with these accounts. All of our accounts are in Entra ID