ThumbsUp.dll failed to register - contact support - on update of Pro 2015 64 bit

I am trying to update SketchUp Pro 2015 on my Win 7 PC but I get:
Module C:\Program Files\Sketchup\2015\ThumbsUp.dll failed to register. HRESULT -2147024703. Contact your support personnel.

RETRY just pops up the same message.
IGNORE ends up not actually installing Sketchup because now I can’t start it - it’s not in the start menu.
CANCEL just terminates the install and I’m left with no sketchup at all.

I did a fresh reboot and tried the installer again but it still failed the same way.

So now I have no sketch up all.
What do I do now?

Hmmm… I appear to have solved it anyway.

I downloaded the latest version again (both files are exactly the same size so maybe that isn’t the problem).

This time I ran the installer as Administrator.
I still got the same error.
I clicked on IGNORE.
The installed finished and it did install the desktop icons and now it shows up in the Start menu so it seems to be OK and working.