After sending fax, you can check the fax history in CamScanner Me- Doc Export - Upload/fax history - Fax.

If you see "sending", please tap "refresh" on top right. If the fax failed, it will return credits. But if you clear cache, the fax record will also be deleted.

The fax will be sent from +1 203 723 3308. If the recipient didn't receive the fax, maybe the fax machine rejected to receive or print the fax.