Record player arm no longer rises automatically?

Hi, I have a question. I have a [Sony PS-LX300H] record player. The record player works perfectly apart from one thing where I need your help. When I put the record on and the tone arm lowerer everything works perfectly but when the record is finished the record arm doesn't automatically move up and then back down. The record arm just keeps moving up to the label which is honestly annoying because normally the record arm automatically moves up and then back to its position but the record player somehow doesn't do that. Do you perhaps know what's wrong? The record player isn't the newest anymore, it's from 94, so it could well be that something is wrong, but to be honest I don't know. I've only had the record player for a good two days and have already changed the rubber rings and fitted a new stylus. I've made everything nice and tidy. I've adjusted the stylus weight and I've also straightened out the play, so I've actually got the play back to normal now I only have this one problem. What could be the cause?