If someone unfollows you, don’t immediately unfollow back. It is more likely that Twitter caused the problem than the person intentionally unfollowed you. Waiting will normally fix the issue.
Twitter keeps locking accounts and forcing people to validate by phone in order to unlock the account. This is not the same as suspension. You merely have to enter a code that is sent by text or voice call. You have no choice in the method they decide to use. While your account is locked, your account shows up to others as following zero people. You have effectively unfollowed everyone, but only temporarily.
Once you validate your account and log back on, you refollow everyone, but if you have a lot of followers this can take quite a long time: hours or days for your account to resynchronize. You will end up ...
Read More at Flat Out Unconstitutional