Custom Keyboard works on mac, not on Pi

Full disclaimer—this is my first arduino project. Apologies if I couldn't find the answer to this anywhere and it was right under my nose.

Main question: **Does anyone know of a significant difference I would have to program/wire around between how a mac would recognize a custom USB keyboard and how a raspberry pi would? **

Here are the details:

I'm using a 3v ItsyBitsy along with a couple of standard buttons and an adafruit 2axis thumbstick to act as a controller for rasplex (on top of openelec) running on a Pi3. The preferred method of input for plex is a keyboard and I'm making a built-in cabinet—I don't want a full keyboard for what amounts to 6 keys of input.

I'm mapping the joystick to the arrow keys and using the buttons to trigger the space bar and esc.

I've wired everything and done the programming. Tests beautifully on my mac.

When I plug it into my Pi, however, the only thing that works are the buttons—the thumbstick doesn't move the cursor in the interface.

I've swapped cables. I've rebuilt the program, I've rebooted the pi. I've started the pi both with and without the USB cable plugged in to try to force the driver to reload. As soon as I plug a standard keyboard back in, the arrow keys work as expected.

Happy to share code if that helps, but suspect it's more likely a voltage or keyboard library issue on the pi. Or maybe there's a line up front that would allow me to identify the keyboard mapping to override whatever the pi is assuming?

Anyone have experience here who's willing to help? Or a pointer where I could find the info on my own?

Thanks!

Happy to share code if that helps, but suspect it's more likely a voltage or keyboard library issue on the pi. Or maybe there's a line up front that would allow me to identify the keyboard mapping to override whatever the pi is assuming?

If the other buttons work, it's most probably no voltage problem.

Most probably it's something in the code. Post it so we can have a look at it. Also post a wiring diagram of the setup so we know what the hardware looks like.

Thanks for the voltage tip—threw a powered USB hub between the two and it works like a charm.

Happy to post code or schematics for posterity, but you pointed me in the right direction. Thanks a ton!