Brushes not spinning - iRobot Roomba 4210 Bagless Robotic Vacuum

Side brush? Main brush? both? How did you find that they are not spinning? To properly test, place the front wheel on the table edge and hold the wheels up in the machine (dont hold the tires) , Then start the clean mode.
If it doesnt spin then you need to open the roomba and remove the motor to see if it is just binded up with lint. If the motor spins with your fingers then test the motor with a power supply to see if it is possibly burnt out. If it works on a power supply then your issue is on the main board and it needs replacing.