Okay, got it working. Thought I’d let anyone else know if they find this thread.
I just reinstalled retroarch using these commands:
Close RetroArch, SSH into your GS and then do
cd ~/.config/retroarch
rm retroarch.cfg
wget https://raw.githubusercontent.com/clockworkpi/GameShellDocs/master/retroarch.cfg
from this thread (Solved) Help here, retroarch.cfg needed
Got video back … For now. Wont try setting up megadrive again probably lol . I seemed to have issues getting genesis megadrive working on my GS. Would like to get it working acuse i love the genesis library (earthworm jim, alladin) which are better than the snes versions.