I bought a Sega Genesis 2 in box with everything included so

>>3284191
buy a wii and softmod it

Put a credit card between a piece of thin cloth. Damp it with rubbing alcohol.
Press it into the game slot.
Should pick up oils and dirt stuff

emuparadise my nigga.

I had a model 2 that did this, a few years back. I never figured it out.
I cleaned the cart slot numerous times, reflowed solder again and again...nothing. I gave up and sold it for parts.
Good luck OP.

Try the above suggestions first, but if that doesn't work ten the pins on the cartridge slot might need to be made tighter. Look up the guides online on how to bend them back to make a tighter connection as this is a common problem with genesis cartridge connectors.