Yes ShaneP, you are absolutely right. It did turn out to be the 64 bit issue!

I had so many problems updating my scripts a couple of years ago when I moved from Server 2008 and Windows 7 to Windows 10 and Server 2016. Most of those issues were to do with registry permissions so I just naturally assumed it was some registry permissions issue even though I checked and couldn't find any issues with the registry.

Really interesting how when one's mind is fixated on the cause being abc, one doesn't consider xyz!

Now that I have it all working, I can fix computers where Firefox is not updating and sort out computers where Firefox is using the wrong ID. Thank you.