new tranny in but wont go anywhere

[tobacco farmer]

I have a 04 explorer it is at the mechanics shop I had them replace the tranny with a jasper. I called for a update and they said there is something wrong with the tranny jasper sent them. It will go forward on the rack but wont back out of the shop. Jasper thinks there is air still in the system but the mechanic says he checked the line pressure.
Im just wondering if anyone else has experienced this when replacing the tranny. Thanks