Downloaded Big Sur. Clicked restart. External monitor screen went black. Now nothing.

LAinNC wrote:

I use an external monitor because my late 2015 27” iMac monitor doesn’t work due to damaged cables. I’ve had no problem using the Samsung monitor (except that I couldn’t adjust the brightness) until I downloaded Big Sur. When the prompt came up “restart” I clicked on it. The Samsung screen has been black ever since. Even after turning the iMac off and on again using the power button. Nothing.

Any help on troubleshooting this would be greatly appreciated.

Thanks.

Linds

Get help with video issues on external displays connected to your Mac - Apple Support
 https://support.apple.com/en-us/HT201177