Connector onto board,plus the rast type entry of the cable into the plug is always worth a poke with something to ensure the wire is seated in the plug.
had this problem yesterday after being there last week and tightening connection on flow meter i left snd it worked for 4 days no problem then had to go again the same problem.i even changed the reed switch on flow meter but no good.it turns out it was the connection on the pcb.