If your stand-alone fax or the fax feature of your MFP/MFD is not sending or receiving.

 The first and simplest check for this problem is to check the phone line. This can be done by calling the assigned fax number of the device; if you hear that age-old fax tone burst, then the phone line is probably good. If the call just rings or goes into a void of silence the fax line could be inactive or you have been given the incorrect fax number.