Applies to



When calling in to Microsoft Teams the Teams client does not ring. The user has the dial pad and can make outbound calls.


Calls fail. The portal shows a 404 Unallocated Number error.


The Teams account and settings must be correct in order for users to be able to make outbound calls.

This error is most commonly seen when an account is new. 

The reason is that the user data configured into the Microsoft platform can take some time to propagate through their system. This can take an hour or so in some cases but is often much quicker. 

Occasionally the Microsoft platform is out of sync or an admin has changed the user's number in the Office 365 portal, which can cause the Microsoft Teams number associated with the user to be different to that set in the service portal, producing a mismatch.


Find out if this is a Microsoft issue.

Within the call log, the following information is visible on a failing inbound call:

2021-05-07 14:57:01 (UTC) SIP processing error Invalid argument 404 

2021-05-07 14:57:01 (UTC) Reason header: Q.850 ;cause=1 ;text="3e5815f1-6343-4602-b941-3653b352e2ba;RNL" 

2021-05-07 14:57:01 (UTC), new state => Closing Error, accepted => Y 404 Not Found

Look for the RNL suffix on the error code, as this is returned from Microsoft 365.



Solution Part 1

Follow these steps: 

1. Allocate a random/different number for the user in the service portal.

2. Click on the sync button to run a fresh sync.

3. Wait for up to twenty minutes for the changes to propagate.

4. Allocate the correct user number.

5. Click on the sync button to sync again. 

This will ensure the correct number is stored against the user in Microsoft Teams. 

It may be necessary to allow Microsoft some time to catch up with the changes made.

If this solution does not work:

Solution Part 2

Follow these steps:

1. Remove the Microsoft 365 Phone System licence from the user in the Microsoft admin portal

2. Wait at least 20 minutes for the change to propagate.

3. Restore the Microsoft 365 Phone System licence to the user in the Microsoft admin portal


This may overwrite the configuration for the user.

If this solution does not work then the customer must report the issue to Microsoft. 

This has to be done by the customer with the issue as Microsoft will only deal with the account owner. 

Microsoft can re-sync the customer's account.

To report the issue to Microsoft:

1. Log in to the Office 365 admin portal at 

2. Go to the Admin icon.

3. On the left hand side menu bar select "Show All" to see the Support option.

4. Create a new support request with an appropriate title such as "Unable to receive calls in Teams (404 error)"

5. Within the detail of the support request, provide the following details:

  • A User email address for one of the users with dial-pad that cannot receive calls

State the following in the ticket:

  • Direct Routing is being used in Carrier Mode (SBCs will not show in the Teams Admin centre)
  • Enterprise Voice is enabled for the user
  • The Voice Routing Policy is applied to the user
  • The User has a valid Phone System licence
  • The user can place outbound calls
  • The correct number is showing on the Teams admin centre and the user’s dial pad
  • Microsoft Approved Direct Routing SBCs are being used.
  • The calling service/trunk is getting a 404-rejection error from Microsoft Direct Routing when sending the call to Teams with messages such as "Reason header: Q.850 ;cause=1 ;text="4c5ea470-5ff3-4489-a9bc-7207c168c5f7;RNL" <- (insert a relevant code here)

If Microsoft request SBC logs then refer to support to have these provided.


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