I kept seeing this dialog when trying to get a briefing AGAIN after not making a trip when I first planned it.
I had filed an ICAO flight plan, but I never activated it. It was a day or two old and the briefing was outdated when I got this message. But I had changed the time of departure to several hours in the future, so "more than 2 hours in the past" was incorrect (or irrelevant).
So when this happens again, how the heck can I cancel the first flight plan and get a new briefing for the trip? I recall finding a way once--it's probably simple enough--but I can't remember it now; and I wasn't able to find any help either in iFly or in the online manual.
The first ICAO flight plan times out eventually, although I don't know how long it takes.
Anyway, this is a MAJOR annoyance. And because I was unable to figure out what to do about it, I'm inclined to call it a bug.