also check the wheels and pickups on your trains as they could be dirty and stop the current flowing if you need more help: https://www.newrailwaymodellers.co.uk/Forums is a good place to start
They actually have that on offer as well at a £1. Hornby Track Rubber
You can get a special abrasive rubber to clean up the rails......might be worth a tr
I dug my old train set out of my mum's loft a while ago as I thought my kids might like it. But the track seems to not conduct any more. I think I'll need to buy a new set with track - so if you know any track bargains please give me a heads up.