How are you getting to the upgrade? Kaspersky perhaps?

Two ways; Thunderbird pops open a dialog to upgrade, and via help > About > [Update to 68.3.0] button. I don't use Kaspersky.

I just noticed portable apps are involved. as they do a strange wrapper thing to make Thunderbird thing things that are not so, I suggest you direct your question to them.

I was thinking of that but the other Thinkpad X1 in our office also has Thunderbird portable, configured the same since it was my machine previousy, and has updated properly to TB v68.x. This machine runs Windows 8.1 while my Thinkpad X1, the one that doesn't update TB from v60.x to v68.x, runs Windows 10. Windows 10 if really funky so I was thinking it has something to do with TB and W10.

As a note, over the past 15 months TB has always updated with no issues, at least up through v60.9.1.

I'm a bit confused....that error suggests an update to a non portable was attempted. www.thunderbird.net is Thunderbird desktop download location - not portable.

Portable app is here and they have not got anything beyond 60.9.1 https://portableapps.com/apps/internet/thunderbird_portable https://portableapps.com/platform/features#updater

Maybe I've missed something or barking up the wrong tree, but I would expect a portable version to only update with a portable version.

Well, of all the portable Thunderbirds I've used (7 I think) Thunderbird periodically updates itself, not the portable version but the executable itself and whatever else it needs. I've always thought that was really cool.

I did see where a fresh install of the portable is version 60.9.1 but installed portables, as far as my experience informs me, updates Thunderbird to its latest version, in this case v68.3.1. This version has been updated on my old Thinkpad X1 (4th gen), with Thunderbird portable installed, and I would expect it to be updated on my new Thinkpad X1 (6th gen), with Thunderbird portable installed, but it is not.

I believe Thunderbird portable uses the actual Thunderbird executable. I installed Thunderbird portable on 06 Sep 2018 and the last update of the Thunderbird executable was 07 Nov 2019. This executable, along with 13 subdirectories and another 93 items, resides in the "App\Thunderbird" subdirectory beneath the "PortableApps" directory that contains "ThunderbirdPortable.exe".

So, I've found the update process to be a direct update of Thunderbird not Thunderbird Portable. Does this make sense?

I will bow out. If you install Thunderbird on your machine and the update does not work, I will be happy to work with you. I have no interest in determining if the portable stuff has issues, and it may well have with the implementation of profile per install and downgrade protection in Thunderbird 68.

Thanks Matt. I didn't mean to cause you to look down the rabbit hole. I've posted to Portable Apps but they're looking at TB. Thanks again,

Just a note... Today Thunderbird updated itself to 68.3.1 after it asked me to. Previous to today any attempt to update (to version 68.3.0) caused an error.

Now, all I need to do is figure out how to find add-ons to do a few simple tasks. sigh...

I to looked as portable apps and lo, they had a bug and would not issue the new update because it broke their wrapper. I assume it is now fixed.