95 dakota transmission problems

I spend around $1200 rebuilding my transmission and still doing the same, it won't shift at all, only stays on one gear(first), i took it to a mechanic shop to put it on a computer and find out that the computer is not working. does this has to be with the transmission not working

sorry dude you need to read the 'IMPORTANT' bit at the top where it say dont writhe anything about cars, this is in the wrong place