Didn't get the achievement from killing the lich king

We killed the lich king in 10 normal raid and we didn't get any achievement. I took screenshots to prove. I rly want my achievement pls help.
https://imgur.com/zyjA5kh
https://imgur.com/K0tPCPT
https://imgur.com/49mYf4b

report it on the bug tracker. you'll have to kill him again to get the achi. warmane doesn't hand them out even if not gotten due to a bug.