RetroPie: Need help with controller + keyboard 2-player setup

I have a controller which I've set as gamepad 1 (first boot). Now I wish to use my keyboard as gamepad 2. I have tried everything suggested in the following: - https://www.reddit.com/r/RetroPie/comments/62g3k6/comment/dfma2ud - https://retropie.org.uk/forum/topic/21002/2-player-support-with-usb-gamepad-and-keyboard In EmulationStation, I can control everything fine with both gamepad 1 (joystick) and gamepad 2 (keyboard) In Super Mario Bros, gamepad 1 works fine for player 1, however, when its player 2's turn, the character doesn't move at all with my keyboard which is gamepad 2.

I use the original power supply btw