My granddaughter is having trouble updating her 2015 MacBook from Sierra to Catalina via the App Store. It has been stuck on calculating the time for over an hour and the blue line has not moved. Has any one any suggestions as to what I can do to assist her
I’d leave it alone for a while yet. Interrupting an update is generally unwise so, if it is going to fail, it’s better if the system can reach that conclusion Itself!
Sometimes there need to be 'stepping stone' installations when doing these big installation leaps. A typical one is to have to install El Capitan before you install later macOS versions. You may also remember the significant Snow Leopard upgrade.
OS X 10.11 El Capitan
macOS 10.12: Sierra
macOS 10.13 High Sierra
macOS 10.14 Mojave
macOS 10.15 Catalina
Sierra follows El Capitan, but due to the major changes with APFS from HFS+ [macOS Extended (journaled)] this upgrade may still need to be done in stages - as we tend to do these in incremental steps the 'Interim Upgrade' necessity is sometimes forgotten.
Unfortunately the only indication of this is the stuck progress bar and grey screen.
CLONE!
As always, a 'known good' clone of the current installation is an essential precaution, and should NOT be skipped [Carbon Copy Cloner from Bombich.org deals elegantly with all the APFS vagaries, 30 day free trial use.]
So what to do?
The simplest method for such a jump is to make a clone (or time machine) backup. Then...
2. Erase the partition Macintosh HD or whatever. At this stage it doesn't matter if you re-format to HFS+ [macOS Extended - Journaled] or APFS. The macOS installer fixes that. Always choose GUID when the choice is offered.
You cannot inadvertently erase the Emergency Recovery hidden sub-system. If you need to erase the complete drive for any reason then you need to startup from a suitable external drive.
3. A new 'Drive' will be created, maybe callled 'Untitled' but you can change this.
4. Now click on re-install macOS -- if you have pressed the right key combination this will install the latest compatible macOS
5. Use migration assistant to migrate al your data and settings to the new setup.
6. Note that with the 64-bit only restriction as well as other progress some of your older apps may not be compatible.
7. Go to the App Store and re-install or upgrade any Apps that are missing etc.
8. Sometimes you might need to do a second App Store visit to check if there are updates to updates - usually only if you are doing step by step upgrades.
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Otherwise...
Starting the mac with these optional keys pressed and held before the chime followed by the specific System re-install is one path, but won't avoid the grey screen if an interim install is required. Don't try to install backwards!!
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Command (⌘)-R
Reinstall the latest macOS that was installed on your Mac (recommended).
Command (⌘) Option-R
Upgrade to the latest macOS that is compatible with your Mac.
Shift-Command (⌘) Option-R
Reinstall the macOS that came with your Mac, or the closest version still available.
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A further twist is that if you download an older installer from Apple Support, running it may tell you that it has been tampered with, or corrupted, and cannot be used. The solution is to go into System Preferences and alter the computer's clock to a week or two after the creation date on the installer package [Get Info] when it should run properly.
The auto-time preference is usually restored after a restart if you forget, but DON'T forget!
Thank you Euan I am getting the laptop next week to work on. Time machine backup first then a SuperDuper backup. I will then restart with option/command/R to get the latest OS for the laptop, it is on Sierra at the moment. It is a 2015 MacBook
Hmmm. your plan may not work, due to the jump to Catalina when an interim install step may be required. This happens even using the ER internet method and a grey screen is all the notification you get. Doing the upgrade via the Internet doesn't remove this issue.
Think hard about doing it the simple way: erase the whole drive using an external drive (your new clone?) to run the show, and then install Catalina from the App store or using the Internet Option-Command-R method. That way the interim jump isn't necessary and you can use your clone or Time Machine backup to migrate data--with the advantage of a clean install as well.
You probably need to go to Apple Support, or try Googling 'macOS Mojave Install'.
This would be a cumbersome method though. The easiest and safest, is to make a Clone of the existing drive or partition, erase the original using Emergency Recover, and install Catalina from the Internet (or App Store). Then migrate your data and passwords etc. from the clone using Migration Assistant. See the first suggestion offfered in my original response.
So much has gone on in macOS since Sierra that a clean sweep would serve you well.
Douglas Cheney 