4l60e to 4l80e swap complete, now no reverse! Googled it and I need help desperately!

I just completed swapping my (rebuilt) 94 4l80e into my 97 z71 that had the 4l60e. I got the wire harness and wired everything up and had my computer reprogrammed and as far as I know I have done everything right. It seems to drive great, however I dont have reverse! It goes through and drive in every gear 1st-Overdrive great, neutral does its thing and it doesnt go anywhere in park. So EVERYTHING works good except reverse. It just acts like it is in neutral, I dont smell anything no smoke and no noises so no sign anything is burning up. It just goesnt go anywhere.

I have been told there is a switch under the dash that if that goes out then you wont have reverse but my reverse lights come on so apparently I can rule that out.

I have also heard that the reverse band could be broken or something but if thats the case it wouldnt drive when I put it in first and it does, plus the tranny was rebuilt so I think I can rule that out.

The only other thing I can think of is the reverse solenoid is bad or loose(the guy that rebuilt it said it "should" be good and that he checked all the solenoids) Im hoping that is what it is because evidently you can fix that without pulling the transmission again. The only problem is I dont know much about this.

Please let me know if you have any pictures, information, or any other Ideas on what It might be! I would really appreciate it. I have already put a lot of work into this and I am just wanting to get my truck going! Thanks!