Were you in an Immortal clam whose reign ended on Sunday?
I’ve seen a number of threads about this from players that were officers / leaders / lieutenants in Immortal clans. When their clans were reverted to being Adventurers on the Monday morning reset following the end of a reign, the clan leader turns them into Shadows, and some of the players (sometimes including the clan leader) get kicked from their clan. Even if they’re invited back into the clan, they’re classed as having changed clans that week so are prevented from taking part in Shadow Wars until the following week.
I’ve not seen any response from Blizzard about this.