Check the following if you cannot send faxes to a specific recipient due to an error.
If the recipient machine does not pick up your call within 50 seconds after the printer has finished dialing, the call ends with an error. Dial using a connected telephone to check how long it takes before you hear a fax tone. If it takes more than 50 seconds, add pauses after the fax number to send the fax. A hyphen is entered as the pause mark. One pause is about three seconds. Add multiple pauses as needed.
If you have selected the recipient from the contacts list, verify that the registered information is correct. If the information is correct, select the recipient in Contacts Manager > Edit , and then change Communication Mode to Slow(9,600bps).