From GTCC about their VitalSource integration:
"Booklog helped us figure it out. The box for “Auto email on MO Shipments” in the SO/MO tab was checked and was looking to send a generic email out that the sale was completed. However our FireWall was not allowing it to send that email, so Booklog would not complete the sale. Meanwhile, the students were getting charged by Verifone and receiving the CODE all ok, but Booklog’s credit card reports were not balancing with the Payware CC reports. "