I cannot locate my customer community user in the account team, hence unable to assign the user to the team. Can we not add community users to Account team? Is there any work around?
You cannot add Customer Community Users in Account Teams. You can only add Internal Users or Partner Community Users to Account Teams. While this is not clearly documented anywhere, a good way to verify this is by attempting to add one in the Account Team.
In LEX, if you try searching for a Customer Community User while adding Users in Account Team, you won't get the User returned in the search result. If you switch to Classic, and try to add a User in the Account Team, you will see the option of only Internal and Partner User (sample screenshot below).