There are various reasons why Reverb would suspend your account or place it under review. The most common reason is that you've got an unpaid Reverb statement, and it is past the 15th of the month.
Other reasons include multiple instances of unacceptable behavior, not fulfilling orders, etc.
In any case, simply reach out here and we can get it sorted out. Depending on the situation, we're able to lift an account suspension after corresponding with you.