When I turn on my iMac, the screen turns on and it makes the usual chime. The loading bar starts to move, but when it gets about half way it gets slower and slower, then the computer turns off completely.
P.S. Might be worth mentioning that it is a boot-camped iMac and the Windows partition is working fine.
iMac with Retina 5K display, macOS High Sierra (10.13.2)
I ended up completely formatting the macOS partition of the hard drive (it was using the old filesystem so I changed it to the new APFS). I re-installed macOS onto the partition and set up the computer from scratch. Luckily I had a backup of the hard drive on another backup disk and also in the cloud, so no data was lost. A bit of hassle but everything seems to be normal now. Thank you for all the suggestions. Ben
I ended up completely formatting the macOS partition of the hard drive (it was using the old filesystem so I changed it to the new APFS). I re-installed macOS onto the partition and set up the computer from scratch. Luckily I had a backup of the hard drive on another backup disk and also in the cloud, so no data was lost. A bit of hassle but everything seems to be normal now. Thank you for all the suggestions. Ben
About the screens you see when your Mac starts up - https://support.apple.com/HT204156
Use safe mode to isolate issues with your Mac (formerly: Try safe mode if your Mac doesn't finish starting up (formerly: What is Safe Boot, Safe Mode? (Mac OS X))) - http://support.apple.com/HT201262
Have you tried starting normally after Safe Mode? I know Safe Mode used to do some cleaning and checking that could clear corrupt items.
You could try reinstalling MacOs.
OS X: About OS X Recovery - Apple Support - https://support.apple.com/HT201314 and related: Disk Utility for Mac: Repair a disk using Disk Utility https://support.apple.com/kb/PH22243
I have tried starting in safe mode and the Mac loads to the safe mode menu correctly. But I'm not sure what to do from here. As for what screen I make it up to in that process, I get as far as halfway on the "Progress indicator" screen.
While in Safe Mode please do the followin.....
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iMac only loading so far
