The shop was fine until yesterday (if I'm not mistaken). I was able to see a lot of recent games there...
But when I tried to use hbg today I found the same as you. All May games were removed for some reason.
What custom fw are you using?
I didn't know they made an MSU cart for the Genesis.... I knew about the SNES one and the library for that is rather large but the Genesis one has very few games