Let's try each of these steps in order until the issue is resolved:
  1. In Configuration, Business Rules, ensure the correct IATS credentials are being used for the transmission file.
  2. In the gift batch, select Tools > Create EFT Transmission File > ensure proper IATS account is selected depending on the type of gifts that are being processing in the Batch (credit cards; debit cards).
  3. Contact IATS to make sure there is nothing abnormal occurring on their end.