Second display no signal

Since the 1703 update, when windows 10 boot to login in screen, the two displays will go into 'power saving' status. Then windows 10 only give signature to main display. Second one no signature unless I do win+p key and select another display mode, then back to 'extend'. The second display will have signal. How to fix this?

Just got answer on another post, it's windows 10's "Turn on fast startup" problem.