Sync will work between 2 separate user Profiles on the same PC and the same Logon User Account even when both Firefox "installations / Profiles" are running simultaneously! IOW, "real time" with a slight almost imperceptible lag of a fraction of a second. Sync also works with "non-concurrently" running Profiles, the typical MO.

I have had two Firefox Profiles running tiled on the screen, deleted a bookmark in one Profile and watched that bookmark get deleted thru Sync almost simultaneously from the other Profile. So quick that I needed to shift my focus to the second browser 'tile' before clicking to delete the bookmark to be able to see it disappear.

You got something else going on there, IMO.

Type about:sync-log in the Location Bar and hit Enter, See if you have any error logs in that Win-7 User-2 Profile. If so, open each of the logs and see if you can figure out what's happening or not happening.

If you want some help "translating" an error log, please post the contents here: https://pastebin.mozilla.org/ Make sure you select a month under "How long should your post be retained?" because the default is one day and that usually isn't long enough to get help for an issue such as this. Then provide the Pastebin URL in this forum thread for your Pastebin page. It may take a day or two to get a response, so be patient while waiting for a reply.

Hi the-edmeister

Thanks for the comments about using "about:sync-log".

I have followed your suggestion and posted both a past and a recent copy of the error log at " https://pastebin.mozilla.org/".

I also noted multiple events similar to "1507167288493 Sync.Status DEBUG Status.login: success.login => error.login.reason.no_username".

Is this error message telling me that FireFox sync can't find the username of the non-syncing win-7 User?

How can this be when both users are logged-on to win-7, and I can have either of them on my screen by simply clicking Start>switch users?

Can it be true that, in my situation, the "syncing mechanism" in FireFox only recognizes one username while FireFox proper recognizes both usernames and can operate normally from each user profile?

If all this speculation is true how do I fix the syncing process.

Thanks for your help

BobWald

The link that you posted doesn't lead to the 'paste' that you uploaded. After you hit the Send button at Pastebin the URL in the Location Bar will be changed to the 'paste' that you posted. Like this: https://pastebin.mozilla.org/9069454

The sync-log error messages are for each separate Firefox Profile or "device" as Sync sees Firefox Profiles. So that message is about the one that isn't able to connect to the Sync server.

Look in your browsing history to see if you can recover the URL for your Pastebin posting and post that URL.

As far as your 2 questions go, "Firefox" only connects to the Sync server not to any other "devices". The "connection" goes thru the server and not to any other "devices".

And as far as "users" on Windows (Logon User Accounts or LUA), that shouldn't affect sync, although I don't know what switching "users" does to Firefox and to Sync. I have always run multiple, simultaneous Profiles with Firefox in the same LUA to use Sync with separate Profiles, and I don't know how switching to a different LUA affects Firefox and Sync.

But that shouldn't make a difference with what seems to be wrong with that => error.login.reason.no_username message. Problems with a different LUA / Firefox Profile wouldn't affect that message. But one thing occurs to me; did you change Device Name in that Profile? If it is the same as the other Win7 "device" that might be your problem.