Our raid member from last raid had locked-out for next raid night in same week.
We were extending raid progress for the last boss, on Wednesday and Thursday we raided with same team, but next raid night (Monday) one of our team member had locked out error and couldn’t go in the raid, no summon, no walk in. What can we do?
Did the member, move realm, faction change or race change?
Nope, done nothing we asked same thing first 
We disbanded, made him leader and tried to go in but now we had the locked out warning and couldn’t go in
Hey Aara,
From your description, it is possible that this player got saved to another raid (usually by going into a new raid on their end) - if you extended your raid ID, your group would have last week’s ID, while this player would have a raid ID from this week.
Not much, I’m afraid. If your group and this player have different raid IDs, you would need to wait for the next reset to continue your adventures together. Sorry. 
Hello, we just had today the same issue, we killed kyveza mythic yesterday, just after the reset. One of the player that we killed kyveza with now has an ID with 0 boss killed and cant join us today. If he tries ton enter raid with us it just doesnt let him enter and if he enters as leader it tells him to accept a 0/8 boss ID and we can’t enter at all. Did you find a solution?