Update - Just going to tear everything out and use this as a rolling chassis to build a new ATV. Bit more of a project than I was expecting, but hey, it'll be fun.

I could use some advice from the experts here. I bought an Xtreme Green UTV from 2014. It's batteries were toast, so I replaced them. It is still not functional, and the screen readout is somewhat nonsensical. I'm trying to find where the malfunction is, and the only thing that jumped out at me ...