ferris 3 wheeler, transmission problem

I purchased a used ferris Pro Cut 3 wheel rider, at auction. When i went to pick it up, it would not go forward or back. If i held the pedal down, it would jerk ahead for a few feet and stop, if you held it down it would do it again. It wont back up at all, the hydraulic reservoir level is ok. Any ideas would be appreciated

Change the drive belt and look at all the pulleys and idlers for free sping and no noise or grinding.