A SIP message with invalid SIP Identity was rejected. Uri: %1 Cause: This can happen if there is the user is unknown or configured ...

A SIP message with invalid SIP Identity was rejected.

Uri: %1
Cause: This can happen if there is the user is unknown or configured incorrectly. This can also happen if the phone number(s) of the user are not configured correctly.
Resolution:
Ensure that the user and phone configuration(s) are correct.