Hi Stephen,

Without knowing what preparation was preformed and a backup done prior to 
attempting the upgrade.
The only thing I can suggest is to perhaps try this:

1. Turn on your Mac, then immediately hold down Option- Command-R to boot into 
macOS Recovery 
<https://support.apple.com/en-us/HT201314?utm_campaign=website&utm_source=sendgrid%20email&utm_medium=email>,
 and reinstall the operating system. 
By using Option-Command-R  will Upgrade to the latest macOS that is compatible 
with your Mac.**

2. Release the keys when you see the Apple Logo or a spinning globe

3. When you see the macOS utilities window, continue to the next section to 
determine whether to erase your startup disk or begin installing macOS.

4. Choose Reinstall macOS from the utilities window.

5. Click Continue, then follow the onscreen instructions. You'll be asked to 
select your disk. If you don't see it, click Show All Disks.

6. Click Install. 
Your Mac restarts after installation is complete. 

Cheers,
Ronni

13-inch MacBook Air (April 2014)
1.7GHz Dual-Core Intel Core i7, Turbo Boost to 3.3GHz
8GB 1600MHz LPDDR3 SDRAM
512GB PCIe-based Flash Storage

macOS High Sierra 10.13.6

> On 26 Jul 2018, at 5:06 pm, Stephen Chape <chap...@bigpond.com> wrote:
> 
> Hi folks.
> 
> A friend of mine has a 2016 MacBook.
> She has today upgraded to the latest MacOS.
> Unfortunately I do not know which OS was previously on it.
> 
> She tells me that when she starts up she gets a continuous black screen.
> But she can hear activity happening.
> I advised her to start up in Safe Mode, but the result was the same.
> 
> She is coming to visit me at 6:30 tonight.
> Has anyone any ideas how we might resolve this please ?
> 
> Regards,
> Stephen Chape
> 
> 
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