We are receiving an error message "The envelope allowance for the account has been exceeded." What does this mean?

Based on the DocuSign Account, there is a limit to the number of envelopes that can be sent during a period of time, usually based on the billing cycle. Sounds like you have sent out that maximum number of envelopes. You would need to speak with your DocuSign Account representative or Sales representative to check what your limit is or to extend your limit.