Key not working
Battery compartment is pressure released and if you press down on the battery compartment the key works fine this is the first thing we would recommend to check.
Key will not fit the lock if it is the wrong key. Likely if it fits the lock it is the right key, they are formed in such a way that if its wrong key it won't fit.
If key opens the battery door it is the right key, typically if this issue comes up it is relating to closing the battery door. If it opens it then it's the right key for both ignition and door. Keeping in mind that the issue is not so much the door per se but more like the seat itself, which has a pressure-release latch. If this latch cannot do its job due to battery not pushed all the way down, battery strap getting in the way, or wiring getting in the way, then the key will not lock the door.
Brakes are spongy or lack of braking
See the Sur Ron Maintenance Tutorial's brake bleeding section
Pedal Kit is loose or grinding
the front fork is loose
You headset might be loose or damaged.
First would be to loosen the top cap of the stem, loosen the stem and the top crown clamp. Try to wiggle the fork a little to make sure it seated correctly and then tighten the top cap of the stem first, this will compress the whole assembly together. Try to wiggle the fork again to see if you still have some slack. If you do please repeat again. Once the front is solid you can start by tightening down the top crown first (do not over tighten the clamp bolts) then move toward the stem and tighten the clamp too. You should be done.
If it still does not feel right replace it, please see this video on how to replace it:
Removing the bolt on the fork for assembly
You unscrew the right side bolt "clockwise" and then unscrew the axle counterclockwise, lift up on the fork to release pressure, and pull the axle out
If you are facing the bike. Take the left cap off. Then unscrew the right side. Take the battery out, so that you can lift the front of the bike easily. Lift, wiggle, and pull out the axle. There are arrows on the axle for unscrew direction. For a visualization please see the Sur Ron Maintenance Tutorial's axle removal.
Brake Rotor Rubbing