OK, that's good information.
The fact that it started making odd noises before it failed may be indicative of some sort of bearing failure, or other fault that increased the load on the motor. It is quite possible that this lead to significantly increased current , or perhaps slower speeds and therefore overheating and failure of *something*
That something could be the motor, the bearings, the electronics, or the batteries (assuming it has a battery pack)
You need to test, as far as you can, to determine where the fault lies.
If it still makes some sort of sound when you try to start it up, then it may be a bearing seized. If the battery is low in voltage (or better yet) won't work in a similar unit, then it's the battery. Motor or controller failure can really only be detected by taking the unit apart and testing the continuity of the motor windings, and the presence/absence of voltage on them when it's turned on.
BEWARE of doing tests with the unit open. If it turns out that the problem is a jam, or if it's a loose wire that you connect up again, then consider what happens if the unit suddenly comes to life at full speed whilst open in front of you. Please make sure you keep all of your fingers firmly attached to your hands, and eyeballs in their sockets, etc.
If you've checked the armature, then I would suggest it's a controller fault. If you can rule everything else out, then we're going to need a series of photos of the controller so we can suggest where to go to next.
