Chosen Solution
iMac 21.5 late 2013 I bought this computer and all was fine. It came with an OS X Yosemite, free upgrade. But, if I run the upgrade I begin having problems and eventually the system fails. I tried to delete the ‘free upgrade’, but couldn’t. I talked for many hours with MAC support and tried resetting my computer several times and deleting all data as well. But, after all that I still can’t upgrade. It works fine as long as I never upgrade… But, this is an old version and I consider it unsafe, so just use it for gaming and never log into anything on it. I need it for other things though… Does anyone know what I can do? It has 8GB, and uses Intel Iris Pro 1536MB.
Take a look at the date on your Yosemite download. Now reset your date and time to a couple of days after that , then install it.
Have you started the computer yet in recovery mode and scanned your hard drive for errors? (Repair permissions and Repair Disks).
Finally, I think I have got it. I reset the PRAM. EMC, checked the clock time and it was on time. But, then I changed the time to 2014 and back again. Hoping that it would work, I then erased the drive and upgraded to Sierra. It seems fine! My notifications flash in the upper right corner of my window, but I think that’s due to the VPN I use. So, I shut notifications off. All is good for now. Thanks everyone!
