I'm having the exact same problem. Maximus Arcade recognizes my joystick and all inputs connected to GP Wiz. I can scroll up and down using the joysticks and launch games by pressing one of the arcade buttons. However, MAME doesn't recognize the joystick or any inputs from the GP Wiz. When I try and change them in settings (Tab -> etc.) and reassign a function, just sits there blank waiting for an input even though I am pressing the designated button.
Any suggestions?
Command-line mame: mame0120b.exe, MAME 0.120, Windows command-line
GP Wiz: GP Wiz MAX 32 inputs USB
PS: Works fine in MAME32 (Windows GUI) however doesn't work in MAME (command-line) when ran by itself without Maximus Arcade
PS2: I copied over the MAME32 config file for my controls to MAME and although it lists the button in MAME (Player 1 Up = Joy 1 Up) still doesn't work.