2012 Yamaha Golf cart stopped now won't charge

We have a refurbished (with new batteries) 2012 Yamaha Golf Cart the kids were riding it and after about 30 min it quit running . I thought they forgot to charge it but when I got it home it will now run fine. But the problem is it will not charge. The charger does it pre check and then says illegal shut down and now doesn't charge. Any ideas? Thanks