Assigning Microsoft 365 Phone System License fails with strange/confusing error message

Contributor

Hello,

 

for internal tests we currently assign the Microsoft Phone 365 License via the Admin Portal manually. All other Licenses are assigned automatically via synced AD Groups.

 

If we now assign the Microsoft 365 Phone System License by hand via we get the error message (Names replaced, tough username@contoso is exactly the same). 

 

The email address username@contoso.com is being used as an alternative email address by user (Lastname, Firstname) username@contoso.com. Use a different email address.

 

We can't add the license via Powershell or AzureAD. In Powershell nothing happens, though the commandlet runs successfully. In AzureAD -> Licenses their is also just a  generic error. 

 

On some users it works on some not. Their is now visual difference eg. with the upn etc.

 

It is also the case with the Audio Conferencing License. 

We have done this many times before with Audio Conferencing and for a couple of users with Phone System  without any problems. 

We have no clue and it seems MS Support also not :(

any hints ?

 

Many Greetings

Erik 

 

 

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