No data output from APM 2.5 Board

Hi I’m not sure if this is the correct forum to ask in, but I’m trying to use what I think is an APM2.5 board with an RC car for a class project, but I’m having problems getting started. I think this board is the APM2.5, but I don’t have documentation. It has an ATmega2560 mcu, it looks like the same footprint at the APM2.5, I was told it has a pressure sensor and IMU on board, and it was previously used with an external GPS module.

I downloaded APM Planner 2 on my Ubuntu 18.04 virtual machine (I also tried it on windows 10). After quite a bit of trial and error, I was able to connect to the board and flash it with the ArduPPM_v2.3.16_ATMega32U2.hex firmware. It says APM flashed but then the calibration screen doesn’t pop up and while APMplanner says its connected it doesn’t look like anything is happening. Then I tried flashing the APMrover2.hex firmware on the board and the ABC LEDs flashed different colors and the calibration screen did pop up. However, I tried calibrating the IMU but the board said it got 0 data points. Am I using the wrong firmware/ where can I find the right files? Right now the board is just being powered via usb and has no other sensors attached to it, so I’m not sure if any hardware is needed. Also, if this is the wrong place to ask please direct me to the correct forum. Thank you for any help!

Its the right place because that Flight Controller is no longer supported and hasn’t been for years. One of these might be the last supported version.
APM Rover

Get a new Flight Controller that is supported by current Ardurover. There are many.