Kohler Command PRO Engine Swapped now it won't start

I have an older exmark 60" zero turn mower that had a bad engine. It worked but leaked oil pretty bad so I had to put about a quart in each time I would use it. This weekend I swapped it with a brand new Kohler engine and after getting everything hooked back up it will not start. When I turn the key it just makes a clunk and nothing more. If someone with more experience troubleshooting can please take a look at this video of me trying to start it I could use some help. I have tried jumping it with my car in case the battery wasn't charged enough but that didn't make any difference. I also checked the belts and I'm not sure what else to try.

https://youtu.be/N1Qb7uxxOZc


Thank you!