Black screen after upgrading Big Sur on iMac 27“
After upgrading my iMac with Big Sur the screen remains black and seems to be frozen. What can I do to restart my iMac?
You may have suffered a hardware failure when the upgrade occurred. Please try shutting down the computer and then restart and hold down the power button for about 15-20 seconds. If it still will not start up, please take the computer to your local Apple Authorized Service Provider to be serviced.