Joe: I don't own your unit anymore as I sold mine due to lack of space on my down-sized layout. If I remember correctly, the motor that rotates it is in the base and drives a shaft that comes into the bottom of the light tower. You may want to remove the bottom cover(s) and take a look in there. Could be a broken wire, etc.
Also, isn't there an "on-off" switch external on the base as well. You may want to check for that as well. Good luck.