Hi there and welcome
Can you power off the mac, hold the SHIFT and with it held down, power it on until you get to the sign in screen
Can you get to this?
ok, now try to sign in and tell me what happens please
ok, can you do the following please
Tell me if you can now sign in please.
ok, what happens when you choose the second option?
ok, Power off the mac
Then start the Mac and hold down the Command and R keys at startup.
Hold these keys until the Apple logo appears. After your computer finishes starting up, you should see a desktop with an OS X menu bar and an OS X Utilities window
choose Disk Utility from the Utilities window, or from the Installer menu if you're started from an installation disc.
Click the First Aid tab.
Click the disclosure triangle to the left of the hard drive icon to display the names of your hard disk volumes and partitions.
Select your Startup Disk (usually named "Macintosh HD").
Click Repair. Disk Utility checks and repairs the disk.
Let this complete and when it has, tell me if you still have the problem please.
you could not get to the utility? can you try a few times please?
You should have then First Aid? you see this?
ok, we will have to the try to restore, do this please and let me know if it then lets you in.
ok, it has lost all its data, it is possible the hard disk has totally failed, but the only way we can check this is an Erase and then a Restore.
It will clear everything on the hard drive, all files but this is not accessible anyway
yes, do this, the restore reinstalls the operating system after you do this
Which options do you have for format?
choose Mac OS Extended (journaled)
what do you now see on the screen?
ok, exit it and tell me what now happens please.
ok, choose Startup Disk, what options do you then get?
ok, go back t Disk Utility please, then do a restore again and restart and tell me if it then starts please.
ok, tell me what happens when it does this please
it is ok, we have confirmed the issue
It is the internal hard drive that has faulted, it faulted during the upgrade
I am really sorry about this and you are going to have to return the mac to have this replaced. It will be covered by the warranty if this has not expired, and the replacement will be done at no cost to you.
I am really sorry about this, and if you have problems, or would like any additional information or assistance, please do not hesitate to let me know.
And if you can take a second to rate my service by clicking one of the stars at the top of the page, then submit, that would be greatly appreciated.
True, if it is out of warranty you need to carefully consider if it is worth the investment to you.
If you need anything else, please let me know
And please remember the service rating via one of the stars at the top then submit so I am credited
Thank you Don