when i try to install Windows 10 on my imac screen goes black
Hi
When i'm trying to install Windows 10 on my iMac ( late 2015) the screen goes immediately black after restart. The windows iso version is newly downloaded, also OSX is lates one with all updates.
Boot camp lets me select ISO, resize partition and do all preparations, however after restart screen is black. Not even any logo or sign of life, just black.
I've tried "option" during boot and select Windows manually also tried to boot Windows installation from usb. in all cases immediately after selecting windows installation my iMAC goes dark ( like in save mode)
Based on power button reaction I can say. its not shut down as before boot it again i need at first keep power button for few seconds. Then I can press power button once more to have some reaction
Any idea is very welcome
Thanks
iMac 27″, macOS 11.1