Check if you get a dial tone on the loudspeaker of your fax machine.
- If yes, try with the loudspeaker from your Dect (push twice the green button)
- If it's working, the headphone from the Dect is defective
- If not, remove the batteries from the Dect and unplug the machine from power, wait for 10sec and put back the power and replace the batteries
- If no, check if the telephone cable is plugged into the socket marked LINE on the machine and from there it's connected directly to the line socket on the wall