Double check if all motor cables are tightly connected on both motor and controller side. Try to power-cycle the controller and see if the motors are now being detected. If the motor LED still doesn’t turn green after boot-up, there might be a defect with your motor. Try to use another motor.
Instead of power-cycling the controller, you can also go to the Connections screen in the app, tap the ‘Update Connections’ button and choose the ‘With Motor Check’ option. This will scan the motor ports of the controller again.
Never connect, or disconnect motors while the controller is powered on. This can damage the internal components of the controller. Motors that are being connected while the controller is already powered on will not be detected until you power-cycle the device.