@kdeck2004 :

Update: I got my controller working again with RetroPi.

Root Cause: I tried two wireless keyboards and hard wired them via USB to the RetroPi. Neither one was recognized.

Solution: I used a regular USB keyboard that I use on my PC to connect to RetroPi. It immediately connected and was in use.

I had to then go into the Bluetooth settings and ‘forget device’ my 8BitDo controller. I then re-paired it using the menu and it worked like a champ. :)

Deleting retroarch.cfg and renaming the other one didn't help. I reinstalled RetroPie with the same image. Installed plugin https://github.com/meleu/RetroPie-joystick-selection. In it I've set detect by name and set Logitech to player1 and Redragon to player2. It worked for player1 in lr-pcsx-rearmed. Not for player2. It is a problem with Redragon gamepad I think.

In plugin I've deleted 2nd gamepad and Logitech now works in all my cores and all my games and in RetroArch menu.

But when I've tried games the very first time, I had only one gamepad (Logitech) and keyboard plugged. And they didn't work in games.

I think it's the problem in RetroArch, that it decides on its own what controller to use for player. And you can't configure it easily.

That plugin is a good solution with detect by name option, it sets the corresponding device for the corresponding player as you want it, not as RetroArch wants it.

But to be sure I need to test it with normal gamepad for player2, not Redragon one.

@buzz I know it works via the wifikey file, but in this case there was no controller or keyboard working and I was referring to the next section (Connecting to Wifi Without a Keyboard (Raspbian Stretch)) where it's possible to configure wifi directly via the wpa_supplicant.conffile on the /boot partition