[magnets]

There's a million things that could cause this.
Here's a list of the most probable
Is you battery charged?
Have you tried a different battery?
Do you have the radio wired correctly?
Is there too much resistance in the drive train?
Did you lubricate your gears?
Do you have an electrical problem?
Is there a loose connection?
Do you have a weird frame short issue or grounding issue?
Have you measured resistance from ground to your frame, and was it anything other than infinity/no connection?