wsa,
When a robot turns on it does a self-test.. If it fails the test it just stops..
They usually move forward and back and then blow a little "volcano" of water out the top. When yours is running the test, if you don't see the volcano of water, then mot likely the suction motor has some issue..
The suction motor can get clogged, or hair can cause the motor to run slow, or not at all.. The manual tells you how to clean the impeller and motor area.
Thanks,
Jim R.