If not running at all, check that there is no mechanical reason for the failure, if mechanically OK or only running at one speed then replace the speed control module.
You can bypass the circuit board and wire it into a relay so the unit will come on when needed. The best thing to do, would be to change the circuit board. A HVAC company should be contacted to preform this task.
The Goodman website provides free user manuals and customer support about any problems with a Goodman speed fan. However I have never heard of these speed fans having any problems but I guess it's possible.
You can get it replaced or checked out by a company. If you are a do it yourselfer then you may check the electrical connections and make sure it's correct.
