Microsoft Teams “User Not Found” Issue Caused by Legacy Skype Attributes

Today I’m bringing a slightly different post. I usually write in Portuguese, but I’m starting to expand the blog’s communication to a broader audience.

In this case, I want to share the resolution of an incident involving Microsoft Teams during a migration from Google Workspace to Microsoft 365 in a legacy tenant.

Scenario:

During the stabilization phase of the environment, some users reported that others were unable to add them to external chats, include them in group conversations, and similar actions.

They simply couldn’t find the user as if the account didn’t exist.

At that point, I thought: “Alright, let’s investigate.”

When I checked the user in the Microsoft Teams Admin Center (MTAC), everything looked normal. However, when I reviewed the Teams settings, I noticed that the user was set to “Coexistence mode”.

Even after attempting to switch the user to “Teams Only”, the change could not be saved.

This started to look like an environment that previously used Skype for Business, where attributes were not properly cleaned up during the decommissioning process.

To confirm this, I checked the attributes via PowerShell in Active Directory and that’s where the root cause became clear: legacy attributes were still populated.

Since this is a production environment, I can’t share full details, but the image below shows the parameters I used for the diagnosis.

After clearing the legacy attributes, I was able to successfully switch the user to “Teams Only”.

Once that was done, the user could communicate normally with others again.