I'm on 1.12.0 now and all my mame games show a "no engine" icon and when I select them there is only the option to update (which never completes)
I'm still getting the can't download mama and RetroArch error as well. Seems these could be related.
I was able to temporarily fix this after I noticed the emulators portion of the AGS settings was blank. I made it look like this (https://forums.polycade.com/d/99-ags-pc-requirements) and it now works. I assume because the emulators wouldn't download it was causing this but this seems to have fixed it for now. No idea if future updates will break it.
Thanks for the follow up here @Atlpitch ! This is likely the result of some server issues we've had lately that have caused downloads to intermittently fail. Should have it fixed very soon!