We have been testing a faxing integration using our sandbox account and just started receiving the message "you did not have enough available calling credits to send this fax".
Looked it up online and found this link https://github.com/ringcentral/ringcentral-faq/blob/master/docs/fax.md that states that it is because we have blown through 1000 minutes of faxing this month. However, using the instructions in the link we checked our account usage and it says we have only used 508 minutes.
Any other reason this could be happening?