Upgrade to High Sierra stalls/fails at “Calculating installation time“ I am trying to upgrade my 2015 MacBook Pro from Sierra to High Sierra.

I downloaded the installer from the Mac app store and started it. The first slightly alarming sign was during a reboot about a minute or two in the process when the screen went black and then displayed white horizontal bars in places on the screen (like a display glitch) for a few seconds before then rebooting and continuing.

It then displayed the Apple logo with a progress bar which then displayed “Calculating installation time”. This remained on the screen and nothing else seemed to progress any further. I left the installer to continue running overnight, but when I woke up this morning it was still stuck in the same place, and the progress bar had not moved.

Realising that the installation had probably failed, I rebooted to try again. Now I cannot get beyond entering my password to unlock the storage drive (SSD), some console errors appear briefly on the screen, and then I get a multilingual message on a black screen to wait or press a key to reboot. 

What should I do now?

Is it:


Try to launch the recovery system (if this has not already been wiped),
Reinstall the existing OS from there (or from USB stick, failing that),
Restore my files from Time Machine,
Try again?


I saw in another post that someone else had problems upgrading, apparently due to having an NTFS driver installed. I have the Paragon NTFS driver installed to allow me to use NTFS external drives. Given that High Sierra has new rules about kernel extensions, which I imagine a file system driver must use, it sounds as though I should perhaps uninstall this before trying to upgrade again?
I finally managed to resolve this problem by attempting to see if I could use MacOS Recovery to reinstall the existing OS, if this was still possible.

Recovering the existing OS seemed not to be possible, but I was able to unlock and mount the laptop's drive (which seemed to be the point where the previous OS upgrade attempt had failed) using the recovery system's Disk Utility, and then use the internet recovery option to install MacOS High Sierra via the internet. 

The installation was successful this time, the drive was converted from HFS Plus to APFS successfully, and my data was preserved.