2010 re ses bought from insurance

Just got it on the road. Sitting since 2015. Put new 91 gas in it yesterday when gas light came on.. drove 15ish miles on old gas.

This morning backed out. Noticed a small backfire when shifting first 2 miles or so....than check transmission came on (no limp mode scroll). I didn't stop, just changed the oil yesterday and put 2 new filters to include the updated trans filter. 2 or 3 miles later I noticed the check trans was gone.

Any comments

Thanks

Phil
Bakersfield