TopCNC TC55H, can't import USB files

I have a Taig CNC mill I got on a trade, and put new stepper motors, drivers, etc on it. Got everything wired up and working, and got the settings tuned in so when I jog 10mm, it moves 10mm. I went with a standalone controller, as I seemed a good solution, and I'm familiar with that from years ago running a Haas mill and lathe.

From the best I can tell, it reads .txt gcode files, and has to be named with a prefix of P followed by 4 numbers. So i've been playing around with different post processors on fusion 360, but when I try to import the .txt file from a usb to the controller, it freezes up. Google searches turns up minimal info on this controller. Does anyone have experience with this controller and how to import files to run?

Thanks

I got some txt gcode to import, but it only imports 17 lines worth, and seems to be generating lines of code non-existent in the txt file. `