Unpairing Repairing to different tivo

New here still trying to learn everything..I have 2 Roamio in two seperate rooms. I use one box to split to different tv's I added slide remotes no problem. I'm trying to unpair the stock remote that came with box A and repair it to box B. I've tried to unpair and repair to box B several times but can't get it to work. It still controls box A. .I hope this makes sense Thanks