Got a "00 A8 Q. Had tranny over haul but car went into limp mode anyone out there help pls!!!!

I am new to this stuff(audiworld)thought this was A8 fourm. I had a tranny overhaul but car is now going into limp mode but if I turn the car off and back on it works and goes back into limp mode just looking for someone who may knew about this and what I might to fix problem