Fix Mac Won't Boot/Start after macOS High Sierra Update 2017
**1. Reset SMC to fix Mac won't boot after High Sierra update**
Sometimes, if the Mac computer cables are not connected properly, you may not be able to boot it normally. So if Mac cannot boot after a system update, you can reset SMC to fix Mac won't boot issue after macOS High Sierra update:
1. Shut down Mac computer and unplug all cables;
2. Wait for a few minutes and then plug the cables back;
3. Restart Mac computer to see if you can enter the system or not.
**2. Force to reboot Mac ...