Error Message:
Error occurred on sending fax
Login not successful. UserName, Password or IP Address failed login validation.
Organization ID: XXXXXXXXXX
Organization Fax Number: 866XXXXXX

If you see this error message, please submit a case to support through contact support page. In case detail, copy/paste the full error you received which should show your Salesforce organization ID and assigned fax number through A5 Fax app. With these details, support team can investigate and resolve for your fax number settings.