Stuck on the BfA War Campaign

I’m trying to do the Horde war campaign and can’t figure out how to continue. I am level 50, I have friendly for all 3 factions, I unlocked the heart of azeroth, and I’ve done all previous missions for everyone on the Banshee’s Wail (apart from doing the Motherlode). I’ve got all my footholds unlocked. Nathanos has no quests for me except to go to Nazjatar and Darkshore. How do I get him to give me the nations united quest?

With Dragonflight, most of the War Campaign’s level requirements were bumped up to level 60. So, you’ll need to level up before you can continue.