No compression

I've had this 2013 prowler 700
in my shop for over a year got it at an auction for cheap only few hundred miles on it but a-arms were all broken and bent. Anyways it started right up and ran good when I got it. Finally got all the arms and suspension together and now it won't start just turns over. It has zero compression.. what would cause that while just sitting in my shop? Appreciate any help. I read there is a compression release.. can that get stuck? Can't find any diagrams on how it works.