I cannot see the Tab Chat on Teams:
Can you cehck in the Teams settings if Chat is allowed?
I think just the admin can see that, right?
@Mike Parker We are experiencing this now, however Chat is enabled in the Teams Admin Center...it was visible and working and suddenly disappeared.
Same exact problem here. No one changed settings and chat appears to be enabled. Chat tab has disappeared for the entire org.
Having the same issue tonight.
Looked at MS health page and the only issue with Teams is with @mentions.
Try log into the Teams with your browser and see if the Chat tab is there.
Logout from the Teams client and log back in to see if the Chat tab returns.