So you did have the original Firefox Sync username, Password and recovery Key?

(just so you know for the future, Firefox sync is not for Backups. It is for synchronizing between two computers, but not ideal for backing up before a reinstall).

He logged in the exact same account with the username and recovery key as the original.

See if there is any data in your Sync account on the server.

https://account.services.mozilla.com/

Once you are logged in and viewing the page with this header - Welcome to the account management portal for Mozilla Services - click on the last item on the left - Request a quota increase - but don't do anything, just view You are currently using .... under the Submit Request button. That will tell you how much data you have on the server.

Maybe your data was inadvertently cleared??

You are currently using 89.7783203125K

That is a good amount of data on the server.

Type about:sync-log in the URL bar and hit Enter.
Do you see the text files? If so, do the name of the file/s start with success-?

Then, click the orange Firefox button and click on the Sync Now button.
Let the Sync process run for awhile - like 30 to 45 minutes and then see if your data has been synchronized to that PC.

There's nothing under log, since the whole computer has been erased and re-installed I doubt there would be anything under profiles

If about:sync-log is empty, my guess it that a Sync hasn't been done to get your data from the Sync server.

Did you hit the Sync Now menu item, as I mentioned?

I did and nothing seems to happen, no dialogue, no loading cursor, no nothing

There is no visual indicator that a Sync is in progress or doing anything, the "indicator" was removed at the time that Sync became a built-in function as opposed to the Add-on which was used as Weave / Sync was being developed two to three years ago. Other than keeping the Bookmarks Sidebar open while the Sync process is running, there's nothing to watch as far a progress.

As I said above - "Let the Sync process run for awhile - like 30 to 45 minutes and then see if your data has been synchronized to that PC. "

I have never seen it take that long, but I don't have very much data in the Profiles where I have Sync activated. I don't have multiple "devices" and have no real use for Sync; I keep up with the progress in the Sync "program" via multiple different Firefox Profiles on this PC and with multiple different Sync accounts.

bestmortgage4u - it might be best if you started your own thread with Ask a new question and provide the requested information. We would like to be able to help monorio1 solve his problem without interruption by seemingly similar problem another user might be having with Firefox.

As Tylerdowner mentioned, Sync isn't made for the purpose of backing up Firefox in preparation for a re-installation of all your software. That complicates things when trying to help a user sort out their problems.

Be assured that next time I'll personally back up my bookmarks and profile, it's been around 30 minutes now and still no bookmark or history, I think that everything might be lost forever. What a shame...

Let it run for (say) another 15 minutes, then close Firefox. When you restart Firefox see if your data is there. If not, see if a sync-log text file has been generated.

I'm gonna be gone for a few hours, I have some work I need to get done this afternoon at a remote location. I'll check back here when I return.

After an hour still nothing. Thanks Ed I'll need to make up for it somehow

See the screenshot - open up Options -> Sync - does it look like this?

Also, does about:sync-log now show a .txt file?
If so, please copy 'n' paste the data from that text file into the Reply box.

Got the exact same thing like in your screen, unfortunately no .txt, no nothing in -log

Sorry, I'm stumped at this point.