The technical manual for your treadmill does not list any error codes. The "FF" code indicates the electronic board in the console is either confused or has failed.
Disconnect the power from the treadmill for 2 minutes or more. If the "FF" remains put the treadmill through the calibration mode. If the "FF" still remains the console will have to be replaced.I am sending you an image with the instructions for putting the treadmill into the calibration mode.