The OP's confusion comes because presumably the tickets are part of a package. So yes, you'll gain access to FP+ at the 60-day mark and not before. Since you're more than 60 days out from your trip right now, the system thinks you're trying to go in and make FP+ for sometime in the next 30 days and thus is saying "hey, you don't have a ticket that can be used in the next 30 days".
It's been mentioned a few times on here that a couple of the "not-really-an-error error messages" on MDE could be reworded to cut down on confusion.
-Rob