Organizations often disable Azure AD accounts when users leave or for other reasons. What you might not know is that Teams then removes the account from membership of individual teams. A background process looks for disabled users and removes these accounts from team memberships. That doesn’t sound too bad, but what’s horrible is when you unblock an account. Teams takes a long time (at least 24 hours) to restore standard teams, it might not ever restore membership of org-wide teams, and private channel membership is removed too. It’s not a good situation.