I ended up spending many hours reinstalling 52.9.1 from scratch and recreating all dozen or so accounts.

The only thing I've lost is my theme which was a simple space theme. Also, emails that were digitally signed by certificates that have expired are showing as invalid and saying that I don't trust the certificate provider. Is there a way to fix that? These are S/Mime certs.

Themes predating v60 have all been removed, though I did find some "full themes" which totally brutalize Thunderbird. The theme I had was basically nothing more that an image at the top.

I have my original profile folder. Is there any way to recover the theme from there?

I realize my suggestion may take time, but I think it may serve you better: - reinstall ver 78, as I inferred that you got that working successfully - backup the profile and then upgrade to 91.0.1 - then backup the profile again and update to 102.0.1 - I suggest another backup and update to 102.15.1 Those steps should get you up to date and compatible at each step. Then, I suggest staying at the release for a few days to get up to speed with changes since 78. The upgrade to 115 is different, as you noticed earlier, but the upgrade should now be simpler.

Hi David, Thanks for that info.

When upgrading to 115.4.1 I followed the instructions from here: https://support.mozilla.org/en-US/kb/upgrading-older-version-thunderbird

I didn't test 78 at all, I simply followed the instructions: Run it at least once before upgrading to 115. I assume that has something with the update of the address book.

Anyway, I will follow your instructions. I've re-purposed another PC as a test PC on which I will do this. There are too many problems with doing this on my main PC.

One of the key reasons I've had to stay with 52.9.1 is the need to be able to encrypt emails only for selected recipients without having to do multiple actions to achieve that. I've used an addon called "Security settings from address book" which totally automates the process. Perhaps I'm not understanding TB115 properly, but it looks on the surface as it will do what I need natively, since the addon no longer works. As this is a daily process, I can't be on a version of TB that doesn't provide that functionality, at least not without going crazy from all the extra clicks.

If TB115 doesn't support this functionality, then I'm pretty much stuffed. I'm stuck on 52 until someone writes another add on to achieve the functionality. I think I'd be waiting for a long time :)

So, in the mean time I would like to recover my main PC if possible. I've got everything working, though I spent all night last night on it (I didn't anticipate the restore would corrupt TB entirely so I hadn't backed up my passwords and address book so I had to do all that from scratch). It had me going for a while when trying to recreate accounts that have long since been retired, then I found that if I didn't enter a password I could create the account. I need to preserve all emails from all accounts for legal reasons.

So, as it stands now I have got 52.9.1 almost back to where it was.

Except for the theme. All I have is a sickly blue color on the top. I have all the original profiles, so is there a way I can copy the theme from the old profile, or perhaps set a background for the tab/address/menu bar area?

to step "way back"

My addons were disabled and I can install them from an xpi file, but not from online. I can't even search and find them online

That is generally a result of firewall issues with the version number. Very common with software firewall installed by antivirus programs.

OR the add-on you seek does not have a valid version for the Thunderbird version you are searching from. Internal searching only shows add-ons that are compatible.

I believe the latter to be the issue. There are now and never was a firewall getting in the way. All themes are supported for v60 and later. I'm on 52.9.1 so that would explain that part of the issue.

The only time I ever had a virus was when I was running A/V software :)

Interestingly, if I search from them from the website and not from TB, I can find the addons and can download the xpi file and install it.

I don't know the possible benefits of upgrading to ver 68, but it appears that addon is supported to that level. If you have concerns about 115, my suggestion is to first download the portable version, setup an account, and test the features you want. That is much safer than upgrading to 115 and then determining that it cannot meet your current needs. The portable version is at https://portableapps.com/apps/internet/thunderbird_portable

My earlier response is the safe way to ensure that all changes in Thunderbird are properly updated, as jumping up several releases can result in incompatibilities.

Thanks again. I've focused on one need. There are actually several. Encryption is by far the most important. The other addons I use are not supported past v60, one is not supported past 52.9.1.

In any case, all of your suggestions are good and I now have a PC I've set up to test all of this. I should have done that in the first place instead of blindly trusting things would b OK and that a restore would bring me back to where I started if needed.

Right now though, I've put 115 on the back burner. My sole focus at this time is recovering the theme that I lost during the process for 52.9.1 I have to look at this TB52 50 times a day.

Fixed it!

Copied the lightweighttheme-footer and lightweighttheme-header files, the lwtheme folder from the old profile. Then, copied the following preferences from the old prefs.js to the new prefs.js file;

user_pref("browser.theme.content-theme", 1); user_pref("extensions.activeThemeID", "default-theme@mozilla.org"); user_pref("extensions.webextensions.uuids", "{\"default-theme@mozilla.org\":\"30036557-5bd8-4356-a40e-2d512379eac5\",\"{d10d0bf8-f5b5-c8b4-a8b2-2b9879e08c5d}\":\"1efc5c9f-de33-4561-af5f-7ec2be7e6bf8\"}"); user_pref("lightweightThemes.persisted.footerURL", true); user_pref("lightweightThemes.persisted.headerURL", true); user_pref("lightweightThemes.selectedThemeID", "87983"); user_pref("lightweightThemes.usedThemes", "[{\"id\":\"87983\",\"name\":\"Galaxy Persona\",\"headerURL\":\"https://addons.cdn.mozilla.net/user-media/addons/87983/Galaxy-Firefox.jpg?1270134806\",\"footerURL\":\"https://addons.cdn.mozilla.net/user-media/addons/87983/Galaxy-Firefox1.jpg?1270134806\",\"textcolor\":\"#ffffff\",\"accentcolor\":\"#949494\",\"iconURL\":\"https://addons.cdn.mozilla.net/user-media/addons/87983/preview_small.jpg?1270134806\",\"previewURL\":\"https://addons.cdn.mozilla.net/user-media/addons/87983/preview.jpg?1270134806\",\"author\":\"Michael_handy\",\"updateURL\":\"https://versioncheck.addons.mozilla.org/en-US/themes/update-check/87983\",\"version\":\"0\",\"updateDate\":1477272789227,\"installDate\":1477224523511}]");

And viola! I have my theme back with all of the other extensions I had.

I am still kicking myself. So dumb to just blindly go an do an upgrade and expect it to work! Now I can go back to testing 115.