Try one or more of the following:
From the home screen, touch Settings > Fax.
In the Fax Mode menu, select Analog.
You may have problems with your phone line.
Are you having issues transmitting your fax messages? Make sure that the document is loaded properly and enter the telephone number manually.
If you experience failure in getting incoming faxes, then make sure that the trays and the toner cartridge are not empty.