I just had this happen to me this weekend and spent a while trying to figure out why my LT wouldn't go to Preset/Stomp mode(my normal modes). I have my entire setlist set up in order of the songs and I'll go into Stomp mode for some songs. Fortunately, it was practice, but I did spend practice time trying to resolve the Mode switch issue. At the time I was running V2.81 and could not find a way to get the Mode switch to work. After running a backup (unfortunately not as current as I would have liked) and being unsuccessful, I found this thread.
After running the 2.82 update, my LT is back to normal and I can use it the way I'm accustomed to using it.