Applies To

Call2Teams - Customer


Phone App is available as an add-on to existing PBX service users. 


This article outlines some of the common issues with setting up Phone App and their resolutions.


Phone App option does not appear in the portal


If the Phone App option does not appear in the portal then the service has not been provisioned to the account. 


Phone App needs to be enabled via the licensing provider. 


Users not showing in the Add Users list

There are two likely causes of this issue:


Users or Tenant not set to Teams Only Mode 

The Sync Now log shows the following type of message:

Excluded 2 users ineligible for Phone App as they are not in TeamsOnly mode for Teams Upgrade.


Review this setup article for remedial instructions on setting a user or the entire account to Teams Only mode: Click here

If this error message still occurs after setting up Teams Only mode then review this article: TeamsOnly Mode still not working


Teams Service is Configured with Large Tenant Mode 

 In Large Tenant mode, any user specified in the base Azure Groups for synchronisation is assumed to have a Microsoft         Phone System licence and therefore is not eligible for Phone App.


Use the setting 'Azure AD Phone App Groups' to specify groups of users whose members will use Phone App. 

  • Ensure the same group is not specified in both Large Tenant Mode AD Group sections.
  • Ensure users do not belong to the core specified AD groups if they are going to use Phone App - they should only be a member of the group detailed in Azure AD Phone App Groups to be eligible for Phone App.


Calls not going through to a Teams user


This issue is a result of the customer Microsoft 365 account not being correctly set for External Access and allowing the         Phone App domain. The logs may report '603 Call Declined' in the call logs.


Allow the Phone App domain on the Microsoft 365 tenant in the external access settings, or allow all domains.

Directions for setting External Access for Phone App are available in this article Phone App (Overview).


It may take several hours for the External Access domain settings to take effect in the Teams admin center.


Call CANCEL does not work as expected - Pools

In some call scenarios when the PSTN/PBX sends a CANCEL through to Phone app the Teams side of the call may continue to ring out for a few seconds with delay. 


This can happen if the PSTN ends a call before the Teams client can accept it, or if the PBX sends a Cancel to say the call was answered elsewhere.

Microsoft have identified that the issue affects tenants who are in a "poolless" state. 

To identify if the tenant is affected, run the following command from a command line terminal:


and check to see if the tenant has a pool value similar to the one shown below:


Affected customers should log a ticket to be notified when the issue is resolved.


User unable a take call off hold


Some Teams clients are affected by an issue with taking a Phone App call off hold (after the user has put the call on-hold).

This is a known issue and will be resolved with a software update.


Affected customers should log a ticket to be notified when the issue is resolved.


iOS users unable to receive inbound or outbound calls

Users with Phone App on IOS devices need to clear Teams app data in order to access and use Phone App again – typically every two hours.

In the event of an inbound call being made during the period where the app requires its data clearing, the call will show as a missed call once the app data is cleared. 

This issue does not affect Teams to Teams calls in the main Teams App.


The likely cause of this is an outdated iOS version. 

The table below shows outbound and inbound call issues and for corresponding iOS versions. 

iOS Version
Compatible iPhones
15.2.1 and AboveiPhone 6s and aboveWorking
15.1 and Below
No Inbound and Outbound Calls


Users should update their device iOS version, to at least 15.2.1

It is advisable to clear the app data after updating the latest version: 

On the phone, navigate to Settings > Teams > Clear App Data

Ensure that the latest version of Microsoft Teams is installed: at least version 4.1.0 

Clear cached app data for the Teams app.


Attempting to use Phone App with a Trunk service (call failure)

Currently Phone App is optimised for operation with the PBX service as a softphone extension.  

Compatibility with Trunk services is planned but not yet available. 

Attempting to user Phone App with a Trunk service will cause the call to fail with an error message.


Using Network view to see error messages

In rare cases users may be required to run a network view whilst trying to place a call with Phone App, in order to see local error messaging.

Method :

This varies between browsers. See the browser support documentation for more details, method for the two most common browsers is listed below:

Chrome/Microsoft Edge:

On the same browser page as the Teams Client, right click anywhere on the page.

Click Inspect on the menu that appears.

At the top of the Developer Tools pane, click the double chevron icon >> to see options.

Select Network

Note: Users must open the network view tab in the browser on the their device, with the Teams client running in the same browser.

Enter a phone number to dial.

Click the the call button. 

The network view should then provide a response error code. 

See the example screenshot below; the Phone App tab is shown on the left, the network view tab with response is shown on the right: