Hold down the Command and R keys, and power the Mac back up again. If it is not responsive and stuck on a screen, hold down the Mac’s power button for several seconds until it gives up and shuts off. You will need to run disk utility with OS X 10.8 Mountain Lion or later. If your iMac is booting up but your operating system will not load, which would happen if the software update you had was incomplete or corrupt, you can fix this in Recovery mode.

If it does, you are all set to go! If not, then proceed to step 6. Shut the Mac down and start it up while holding down Shift. Safe Boot limits what checks and functionality your Mac does during startup, and performs certain diagnostics. If you have any other monitors connected, you will want to remove those too. Basically, you will need to check the power supply to your iMac, confirm cables connect securely and remove all display extenders and switches and other devices. If your display does not work, then you may have a display hardware issue. If that does not work, go on step 3.įorce your iMac to restart by holding down the power button for ten seconds. This can range from printers to USB drives that could have faulty software or not be compatible with your computer. You might even get free or next day shipping. All you have to do is buy an Apple power cable. Fixing a power cable situation is simple. Do you have a pet? Sometimes you have a chewed wire that just cannot supply power. Is the charger working? You may need to use a different power cable or adapter. If your iMac turns on but does not start up, go straight to step 2. You should hear a small startup chime, perhaps some fan or drive noise and then some slight color change on the display. Check to see if your iMac is turning on and receiving power (hardware issue), but not starting up (software issue typically). Not starting up and not turning on are two different issues. Simple enough but this is important to know. For some users who installed the MacOS High Sierra update before the security patch was released a week later, this software update could have stuck your computer. Fixing this and getting your computer back up and running may be quick or take a while depending upon the problems that need to be addressed. When your trusty iMac does not turn on, it is easy to get panicked. Have you been alarmed to see your iMac suddenly stopped working after you installed a security update or used new software? Here’s what you can do.

Mac won39t update software