Firefox 72.0.2 is the last version that supports key3.db, so you can install this version instead of 68 ESR (68.12.0) to make Firefox create a matching logins.json and key4.db that you can copy to the profile folder of the current release.

• https://download-installer.cdn.mozilla.net/pub/firefox/releases/72.0.2/

Make sure to use this version with a new/separate profile (Firefox would probably refuse a 93 profile).

• https://support.mozilla.org/en-US/kb/profile-manager-create-remove-switch-firefox-profiles

Thanks for the suggestion. I downgraded to 72.0.2, created the new profile, allowed it to create a new key4.db from the old key3.db, upgraded to 93, copied the key4.db to my (old) default profile (it did not create a new logins.json) ... and it's still telling me it has no saved logins. Firefox 93 is not only not giving me any of my old saved log-ins ... even when I log in fresh and tell it to save the password, it goes through the motions ... and then it's not there the next time.

You need to copy both logins.json and key4.db from the 72.0.2 profile to the 93 profile. Key4.db stores the encryption key and logins.json stores the encrypted logins (logins.json and key4.db need to match).

I have now downgraded and upgraded several times (because Firefox kept trying to update every time I'd downgrade, even though I'd set it not to).

This is where we stand. I currently have two profiles: the original one created upon the original installation of 93, with settings and bookmarks copied over from my old XP machine (version 52) ... and the latest new profile created in 72.0.2, and subsequently upgraded. The second profile has my functioning passwords. The first one -- even though the key4.db file and the logins.json are identical -- will give me bookmarks and settings, but no passwords. At one point I got a pop-up telling me to input my primary password if I wanted to see passwords, but that quickly disappeared. So I'm thinking that the only way to resolve this is to copy the necessary files for my bookmarks and settings from the original profile, to the one with the functioning log-ins. Your thoughts? And if you agree, which files should I copy over? Thanks for all your help.

Like I wrote above, you need to transfer two files, logins.json and key4.db, for the logins.

They WERE transferred. And then copied over. Several times. As I wrote above, those two files are identical in the folders for both profiles. I have done this several times, and each time, the passwords do not work in the original profile, although they do in the one established in 72 and upgraded to 93. There is no logical reason why it doesn't work ... but it doesn't work.

I copied all the relevant bookmarks and settings files from the original folder to the one with functioning passwords (after backing up all the previous entries). I now have a completely working profile. Thanks.