I know this was a month ago but I had that same exact problem. Update a TIU and remote and then could not get them to see each other again.
Flashing lights told me it thought it was address 4 even if you factory defaulted it, it stayed at 4. Out of frustration I took another remote that wasn't updated and it still was able to read the version of the TIU that had been updated to 6.1. Used the old remote and changed the TIU address from 4 to address 1 and now the upgraded remote 6.1 sees the upgraded TIU 6.1.
Hope that helps someone else because I spend a bunch of time reloading TIU and remote over and over with no loading errors but it wouldn't connect because of the address conflict. And you couldn't change the address in the updated TIU from the updated remote.
