An urgent request

So, picked this up a couple of days ago on my horde druid, did it, got to Icecrown, was able to accept and complete the daily quests. Tonight I log in on my Alliance druid, recently leveled to 50, no quest available.
So what am I missing here? Are there some kind of pre-quests to being able to get this quest? Perhaps you have to do the BFA war campaign?
And… in researching this I understand there is some kind of scourge invasion? Where’s that at? How does that happen, I haven’t seen any evidence of an invasion on either horde or alliance?
Edit: I have tried logging on my older characters that I didn’t play during BFA and for all of them this quest is available. Maybe this is an issue for new characters only?