The last two time I took my 2015 polaris sportsman 570 out for a ride, about 30 mins into the ride it started to run funny I would he in high and when I'd hit the throttle the engine would review but I would only move slow. Any ideas on what it could be and how to fix it?

 

First thought that comes to mind is the belt and clutch area.That's where power from the engine goes first,then from there power is transferred to the gear case then to the drive shafts. If you've been riding in high range at low speeds or pulling loads in high range doesn't take much to glaze/burn a belt which can cause slipping and loss of power to the wheels.