IPega PG-9055 buttons undetected in emulator

[newzilla7]

I have a Raspberry Pi 3 Model B with RetroPie 4.0.2 (installed from the RetroPie website by writing to the SD card). I successfully connected the IPega PG-9055 and set it up in EmulationStation; all of the buttons are completely functional in EmulationStation. Once I boot up a game, however (Pokemon Red in the default GB emulator), the start, A, and B buttons stop responding. The dpad still works. I am unable to determine if any other buttons are not working since it's just a GB game.

Does anyone have any advice or suggestions? I've only found information for the PG-9025, or for previous versions of RetroPie.

Thanks!

[meleu]

@newzilla7 I have an ipega PG-9023 and solved this same problem doing what I said here:
https://retropie.org.uk/forum/topic/2719/keyboard-stopped-working-after-i-played-around-in-the-controller-config-in-rtgui/2

Some other guys (like this one) solved changing the retroarch.cfg input_driver to sdl2 (rather than udev).