See if this helps. https://support.mozilla.org/en-US/questions/1269873#answer-1259076

Thank you christ1. Below is a log of precisely what I did while trying to follow the instructions you linked to. I hope I interpreted everything correctly?

It may take a few days (until Thunderbird next tries to update) to find out whether or not it worked.

1. In C\ProgramData\ open the Mozilla folder (named Mozilla followed by a string of characters) 2. Open the "updates" folder. 3. There are two folders inside, one for Firefox and one for Thunderbird. Identify which is which. 4. Open the folder belonging to Thunderbird. 5. This contains an "updates" folder and several files. (I observe that the "date modified" for most of the files precedes the upgrade to v102. There is also a "backgroundupdate" folder but it was last modified several months ago.) 6. With Thunderbird closed, create a new temporary folder. 7. Move the "updates" folder, updates.xml and update_config.json into the temporary folder. 8. Re-open Thunderbird.

Unfortunately it did not work.

I see that another person with the same problem made a support request at https://support.mozilla.org/en-US/questions/1389993 and received advice from contributor and moderator Wayne Mery.

When I have time I will try following the advice provided therein.

Like the person who submitted the request linked above (gmsherry), I use the free version of AVG anti-virus. The local technician I have been using is extremely adamant that it is the best product available, and while I have no personal attachment to it I don't feel comfortable making decisions about security software without expert advice.

Wayne Mery advised gmsherry to perform a test with the error console and paste results using the filter AUS. Here is what I get when I perform the same test.

13 hidden AUS:SVC UpdateManager:_loadXMLFileIntoArray - XML file does not exist. path: C:\ProgramData\Mozilla-1de4eec8-1241-4177-a864-e594e8d1fb38\updates\D78BF5DD33499EC2\active-update.xml AUS:SVC Creating UpdateService AUS:SVC Logging current UpdateService status: AUS:SVC UpdateService.canUsuallyCheckForUpdates - able to check for updates AUS:SVC UpdateService.canCheckForUpdates - able to check for updates AUS:SVC getCanApplyUpdates - testing write access C:\ProgramData\Mozilla-1de4eec8-1241-4177-a864-e594e8d1fb38\updates\D78BF5DD33499EC2\update.test AUS:SVC isServiceInstalled - returning true AUS:SVC shouldUseService - returning true AUS:SVC getCanApplyUpdates - bypass the write checks because the Windows Maintenance Service can be used AUS:SVC isServiceInstalled - returning true AUS:SVC shouldUseService - returning true AUS:SVC getCanStageUpdates - able to stage updates using the service AUS:SVC Elevation required: false AUS:SVC Other instance of the application currently running: false AUS:SVC Downloading: false AUS:SVC End of UpdateService status AUS:SVC isServiceInstalled - returning true AUS:SVC shouldUseService - returning true AUS:SVC getCanStageUpdates - able to stage updates using the service AUS:SVC isServiceInstalled - returning true AUS:SVC shouldUseService - returning true AUS:SVC getCanStageUpdates - able to stage updates using the service AUS:SVC Checker: checkForUpdates, force: true AUS:SVC Creating UpdateService AUS:SVC Logging current UpdateService status: AUS:SVC UpdateService.canUsuallyCheckForUpdates - able to check for updates AUS:SVC UpdateService.canCheckForUpdates - able to check for updates AUS:SVC getCanApplyUpdates - testing write access C:\ProgramData\Mozilla-1de4eec8-1241-4177-a864-e594e8d1fb38\updates\D78BF5DD33499EC2\update.test AUS:SVC isServiceInstalled - returning true AUS:SVC shouldUseService - returning true AUS:SVC getCanApplyUpdates - bypass the write checks because the Windows Maintenance Service can be used AUS:SVC isServiceInstalled - returning true AUS:SVC shouldUseService - returning true AUS:SVC getCanStageUpdates - able to stage updates using the service AUS:SVC Elevation required: false AUS:SVC Other instance of the application currently running: false AUS:SVC Downloading: false AUS:SVC End of UpdateService status AUS:SVC UpdateService.canUsuallyCheckForUpdates - able to check for updates AUS:SVC UpdateService.canCheckForUpdates - able to check for updates AUS:SVC waitForOtherInstances - beginning polling AUS:SVC waitForOtherInstances - no other instances found, exiting AUS:SVC Checker:getUpdateURL - update URL: https://aus.thunderbird.net/update/6/Thunderbird/102.3.0/20220914215727/WINNT_x86_64-msvc-x64/en-US/release/Windows_NT%2010.0.0.0.19044.2006%20(x64)/ISET:SSE4_2,MEM:3962/default/default/update.xml?force=1 AUS:SVC Checker:checkForUpdates - sending request to: https://aus.thunderbird.net/update/6/Thunderbird/102.3.0/20220914215727/WINNT_x86_64-msvc-x64/en-US/release/Windows_NT%2010.0.0.0.19044.2006%20(x64)/ISET:SSE4_2,MEM:3962/default/default/update.xml?force=1 AUS:SVC Checker:onLoad - request completed downloading document AUS:SVC Checker:onLoad - Getting sslStatus failed. AUS:SVC Checker:onLoad - there was a problem checking for updates. Exception: TypeError: this._request.responseXML is null AUS:SVC Checker:onLoad - request.status: 302 AUS:SVC getStatusTextFromCode - transfer error: Update XML file not found (404), default code: 404

The first suggestion offered was to uncheck "Enable QUIC/HTTP3 scanning" in AVG web shield settings. This did not work for gmsherry and strikes me as a bit risky. The next suggestion offered was to add aus.thunderbird.net and www.thunderbird.net as exceptions in AVG settings. Should this be my next action? Would appreciate confirmation. (It's getting late here, I'll try it tomorrow unless advised otherwise.)

re The next suggestion offered was to add aus.thunderbird.net and www.thunderbird.net as exceptions in AVG settings. The reason you keep being asked is because although the program is updated, the history log is probably not updated and it keeps trying to access server because it thinks you have not updated according to it's history record but your Anti-Virus is blocking access.

So please add aus.thunderbird.net and www.thunderbird.net as exceptions in AVG settings. You may have to wait until next update, but it should fix once it has got access. This has fixed all the cases I've come across.

It's affecting those using Avast and AVG as far as I'm aware.

Done.

This worked for me. Thank you very much! :-)