This is a good thread to follow (it saves me typing):
https://www.svrider.com/forum/showthread.php?t=190657
briefly - check the green connector under the tank, it is a common failure point.
If that's ok, try shorting together the two heavy duty contacts on the starter relay (the lowest connections in the photo in post #2). The engine should turn over (make sure it's in neutral).
Note: there is a lot of current flowing here so use a jumper cable to bridge the connector. Only a brief connection is required to verify the starter motor will work and touching the connectors will generate a spark. Be careful.