Have you tried cleaning the contact tabs? I have fixed many carts by doing the following. Use a pencil erasure to carefully rub the contacts, length ways NOT cross ways. Keep at it until they look cleaner. Then use 90+% IPA or contact cleaner to finish.
I have never come across a cart for any system ever that was just plain dead. I’m sure it can happen though. I have however encountered many that were dirty in one way or another (just plain filth, and or corrosion), cleaning has fixed every single one so far.