What version of MAME are you using? If its pre 0.173 you need to remove the keyboardinput commandline from the manage emulators/MAME screen. And if it is a old version like that do not use a current MAME emulator, most games wont work.
Came here with the same issue, this post helped me get back up and running, thank you neil9000!
Many roms stopped working
in Troubleshooting
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Came here with the same issue, this post helped me get back up and running, thank you neil9000!