These are the problems I have with my Mavic Air:
I have re-calibrated my controller and the drone via DJI Asssistant 2, yet I keep getting a Main Controller Data Error. I have had no crashes or hard landings.

I will share with you the messages I am getting when I hit "go fly" via dji go 4:
1 - "Main Controller Data Error."
2 - Gimbal cannot receive main controller data."
3 - "Accelerometer failed."
4 - "Gyroscope failed."
5 - "Check "Overall Status" in Main Controller settings."

I took screen shots of all these and will include them.

I have tried to calibrate the compass, but when I spin the drone, noting happens. I have also tried the IMU calibration and when I hit the "start" button, nothing happens.

Any ideas of what I can do next to rectify this problem?

Hi. I am sorry for the trouble this has caused. Upon checking the said error. If you have completed the firmware refresh using the DJI Assistant 2 on the drone and the issue still persists. I would recommend for you to contact our designated DJI support team at (https://www.dji.com/support?site=brandsite&from=nav ) to start a ticket for further diagnostic, analysis and repair. Please note that the repair cost will depend on the said warranty period of the drone otherwise, valid charges will apply. Again, I am sorry for the trouble. Thank you.