The simple explanation could be the switch might be off. If the switch is ON, maybe the power might be off at the electrical panel. Check to see if any circuit breakers is not tripped or fuse not...
You can go to Lowe's. Lowe's is a great store for this type of thing. It was made just so that you can find outdoor products like outdoor ceiling lights.
If you buy it new it will most likely come with a mounting bracket. The bracket will usually go on to the handlebar, but might also be intended to wrap around one of the front fork legs. Older lights...
maybe it is an outdoor activity sensor light fixture and when you go inside and there is no activity outside so the light automatically shuts offIf it is a regular romex powered fixture that operates...