I was wondering if anyone has come across this, or whether someone can replicate it.
I've been banging my head against a brick wall all morning trying to figure out why my formatting rules weren't working.
Turns out they were, but I was only previewing the form in the App and Rule changes weren't being implemented, although other controls I added and changed were.
Once I save the form (not publish) and then Preview it again, the rule implements.
I'm on O365, developing a form for the Mobile app in tablet mode and specifically I'm dealing with formatting rules, although it may apply to validation rules too I guess.