Very little goes wrong with these regulators.
The number one issue is one of the window retaining bolts falling out,
causing the window to tilt.
Based on your description, though, I'd suspect the motor may be done.
Plug the switch back in and and try to lower the window while whacking the
motor with a wrench. If the window lowers, the problem was the motor. Of
course, for the nonviolent types, you could simply unplug the motor, and
check for a 12V differential at the connector when the switch is