I have a Sega 32x that I bought off ebay as not working. I have tried it in a Megadrive Genesis, with and without MegaCD and also in a Megadrive II with and without MegaCD. Passthrough (with Genesis games) works fine. I have three 32x Carts (Starwards, Virtua Racing and Doom) and none of these work. The Sega copyright screen appears but then nothing.
I have cleaned and tested continuity on all the connectors and also on the white ribbon cables. Everything seems fine.