Rebuilt transmission installed is not shifting properly

Okay, so my second gear disc snapped in my transmission so I went and got a used rebuilt one. Went in without a hitch but as soon as everything is hooked up my speedometer stays at 0 and the truck won’t shift in drive. I can manually shift between first and second but no third it acts like it’s not there just revs out. I did some digging and saw that it could be the speed sensors on the transfer case so I replaced both of them. The guy I got the transmission from swears up and down that it’s a good transmission. Also have an abs light on but I doubt it has anything to do with it. Looking for suggestions on what to do next. I do not know if maybe one of the speed sensors isn’t getting any power sent to it? Tried looking into that and no where would tell me anything about it. Also brought it to a shop and they charged me $400.00 to tell me they can’t figure it out.