Fruit Machine Chat

There is a plastic 4 pin connector loose, looks like it should go somewhere but cant seem to find where. Any idea's where it should be connected

Hi Everybody I have just bought a Barcrest Each way Nudges machine, It works fine on free play however when i set it to cash play, i get the 'hey check it out' sound and the error ALARM 17-83 PND OPTO BLOCKED AT START Im at a loss as i dont know a thing about fruit machines, so any help would be mos...