Cushman 1200 Gas will not move when in reverse

Cushman 1200 Gas will not move when in reverse

I have a 2015 gas Cushman 1200X. It doesn't want to move in reverse, that is when I press on the gas it will click and try to back up but just will not quite go. On occasion it has kinda started the same in forward. Is there some adjustment on a belt or what?