A troubleshooting guide to Garmin Express 7.16 installation issues

2. Once Express 7.16.x.0 is installed, a “We're unable to add this device” message may appear. Being that the case, the cause is probably a stricter compliance (or simply a bug in 7.16.x.0, I am not quite sure as I did not really investigate this specific problem) to the .NET Framework’s locale/culture which may happen in the event there are unsupported and/or customized regional settings. What to do (a quick workaround):
a. From Windows 10/11 Control Panel, select “Region” and, from the drop-down menu, select “English (United States)”. Move to the “Administrative” tab, select “Copy settings”, check “Welcome screen and system accounts” and “New user accounts”, press “ok”, log off and log back on. Note: you may need to set the language support for legacy (non-Unicode) programs to “English (United States)” as well (this is done from the same “Administrative” tab), however I suggest to do this in the event the inability of adding a Garmin device persists.
b. Run Express and add your device: it should now be possible to register your Garmin device to Express, shortly followed by the request to log back into your Garmin account. Repeat this step until all your devices are added again.
c. Go back to the Control Panel, select “Region” and revert your settings as they were before changing them. Log off and back on. Note: other regional settings may work, however I haven’t done any further test.

3. In the event #2 doesn’t work, a VPN connection could address the issue (exit countries I have tested: US, UK, France, Germany): enable it and follow #2.b, after which you can disconnect said VPN.

4. If all else fails, uninstall 7.16.2.0 (select “Delete all Garmin Express files from your computer” before uninstalling) copy back %localappdata%\garmin and %programdata%\garmin from the copy/backup you made in #1.a and install Express 7.15.x.0 from %programdata%\garmin\CoreService\Downloads\Application\ express-windows.7.15.x.0\omt\express\windows\7.15.x.0\uuid\garminexpressinstaller.exe (note 7.15.x.0 indicates your previous version, i.e. 7.15.2.0 and uuid in the form of a 32 digits hexadecimal number, i.e. a250803b456b9f9711f2e3b7d740a0b3) - this will restore your previous version all all the data.

Note: the error described in #1 can also caused by the .NET Framework’s issue/Express bug described in #2 (the installer, although unlikely, could also be affected). It might be interesting (again, I haven’t tried), to follow the operations described in #2.a before upgrading.

Sorry but I'm an exception to your statement "Apparently, Express 7.16.x.0 cannot upgrade a 7.15.x.0 installation," I am running 7.16.2.0 after successfully upgrading from 7.15.0.0 to 7.16.0.0 (30 Jan 23) to 7.16.1.0 (01 Feb 23) to 7.16.2.0 (22 Feb 23).  All were trouble free updates on a Windows 10 Pro machine.

In the event you skipped it, the final note (the error described in #1… etc.) describes your case, then (though I haven’t tried) being your Windows’ locale supported (not customized, etc. – i.e., “English (U.S.)”): that’s why you did not experience any problem. Alas, none of this is mentioned on the official FAQs.

@JohnfromPA

Worked fine for me too