Hey all, first and foremost... sorry if I'm posting in the wrong area, still kind of a noob. Anyways I'm looking for a little SMS help

I picked up a SMS system today at yard sale as my current system is on its last leg. I tested the system and alas it will play cards, but not a single cartridge. It won't even boot up its internal game, it just has a welcome screen telling me to insert a cart.

Initially that same welcome screen would appear with a cart already inserted, after several cleaning attempts I was able to get to the software error screen. At one point I managed to get Fantasy Zone to start up by applying pressure to the cart while inserted, however the game froze as soon as that pressure was eased.

I'm not much of a technical wizard, so any help would be much appreciated