Server Shutdown? - 5:30pm PST time

It says in Bnet that there is a server shutdown 7am PST time but not that theres one at 5:30pm PST time the night before. Im trying to do keys on my Evoker to be able to get a vault for the last time in Shadowlands and i just got kicked out of the game due to [Server Shutdown]. Anyone know the reason why?