This actually helped:
1 year ago
OK I figured it out. I had to set the hotkeys manually rather than rely on the autoconfig.
For anyone else out there with this issue, what you need to do is open the RetroPie menu. Open RetroArch.
Go to Settings>Input>Input Hotkey Binds.
Go down to Quit RetroArch, and set that to your Start button.
Next go down to Enable hotkeys, and set that to your Select button.
Go back up to the Main Menu within RetroArch.
Open Configurations.
Save Current Config.
Back out and exit RetroArch.
You're good to go now for most emulators.
https://www.reddit.com/r/RetroPie/comments/5t44qq/unable_to_exit_emulators_help/