The new version of Sync only works with the latest Firefox and you can't use both the old and new Sync at the same time. So in order to create a Firefox account and sign in to the new Sync you'll have to unlink all of your current devices from the old version of Sync. Step 1: Unlink all of your devices from the old Sync

On a computer:

   Click the menu button New Fx Menu and choose Options
   Select the Sync panel.
   In the Sync panel click Unlink This Device.
   Click OK to close the Options window
   Restart Firefox. 

On an Android device:

   Open your device's Settings app (not Firefox's Settings menu).
   Under Accounts or Accounts and Sync, tap on Firefox.
   Tap your account name (usually your email address) to view the account settings.
   Tap the menu at the top right corner of your device and choose Remove account. 

Step 2: Update all of your other devices to the latest Firefox

   Update Firefox on computers.
   Update Firefox on Android devices. 

Step 3: Create a Firefox account

On a computer:

   Click the menu button New Fx Menu and choose Sign in to Sync and follow the instructions to create your account. 

On an Android device:

   Tap the Menu button (either below the screen on some devices or at the top right corner of the browser) , select Settings (you may need to tap More first) and then Sync. Follow the instructions to create your account. 

Note: You can use the same email address that you used to set up the old Sync. Step 4: Sign in to Sync on your other devices

On a computer:

   Click the menu button New Fx Menu and choose Sign in to Sync.
   Click Get Started and then choose the Already have an account? Sign in. link at the bottom. 

On an Android device:

   Tap the Menu button (either below the screen on some devices or at the top right corner of the browser) , select Settings (you may need to tap More first) and then Sync.
   Tap Get Started and then choose the Already have an account? Sign in. link at the bottom.

You can check the about:sync-log page for errors and check the most recent reports if any present for issues with logging in.

Current Firefox releases store the Sync login data in the signedInUser.json file in the Firefox profile folder.

You can use this button to go to the currently used Firefox profile folder:

• Help > Troubleshooting Information > Profile Directory: Show Folder (Linux: Open Directory; Mac: Show in Finder)

After disconnecting my devices, I was not able to use my same email address to set up a new Firefox Sync account. So, I ended up deleting my account altogether and I was then able to set a new Firefox Sync account using the same email. But unfortunately, even after setting up and then synching to the new account, I am still having the same problem where when I open up the Firefox browser it will not automatically synch. I am forced to manually sign in each time with my password to connect and then sync. At this point, I am thinking of just resetting Firefox to see if that helps.

I'm seeing this as well and get a Master Password prompt each time Firefox is started, so it looks that things have changed in Firefox 34. If I cancel the MP prompt then I see an error log with a failed login.

Sync.Service	DEBUG	In sync: should login.
Sync.Status	DEBUG	Status.service: success.status_ok => success.status_ok
Sync.Status	DEBUG	Status.service: success.status_ok => success.status_ok
FirefoxAccounts	INFO	returning partial account data as the login manager is locked.
Sync.BrowserIDManager	INFO	Waiting for user to be verified.
FirefoxAccounts	DEBUG	already verified
Sync.BrowserIDManager	INFO	Starting fetch for key bundle.
Sync.BrowserIDManager	INFO	_fetchTokenForUser has no keys to use.
Sync.BrowserIDManager	INFO	Background fetch for key bundle done
Sync.Status	DEBUG	Status.login: success.login => success.login
Sync.Status	DEBUG	Status.service: success.status_ok => success.status_ok
Sync.Service	INFO	Logging in the user.
Sync.Service	DEBUG	Fetching unlocked auth state returned service.master_password_locked
Sync.Status	DEBUG	Status.login: success.login => service.master_password_locked
Sync.Status	DEBUG	Status.service: success.status_ok => error.login.failed
Sync.SyncScheduler	DEBUG	Clearing sync triggers and the global score.
Sync.SyncScheduler	DEBUG	Couldn't log in: master password is locked.

To further update this issue, I did reset Firefox. But that didn't resolve the problem. Clearly, Firefox will no longer automatically connect to Firefox Sync upon opening the browser, with this latest v34.0. I hope this can be fixed, as it is frustrating to have to manually sign in to Firefox Sync each time.

The only thing I haven't tried yet, is to adjust my configuration settings. I was hoping not to have to do that, but I will try unchecking the option to delete preferences automatically when the browser closes. If that, or any other adjustments to my browser settings helps, I will update that info here.

Thank you to all who have responded to this issue.

As a side note, I don't know why I continuously misspell the word 'sync'. Some mental deficiency I have going on, I guess. I apologize.

Unchecking the box beside the 'Saved Passwords' option, in the 'Settings for Clearing History' window, appears to resolve Firefox Sync being able to connect automatically upon running the Firefox browser.

There must have been some exception previously, where Firefox saved the Firefox Sync password, despite Firefox being configured to delete saved passwords upon closing. Even though I don't generally wish to save passwords, I would personally consider the Firefox Sync password a reasonable exception. Therefore, I hope Firefox can ultimately be restored to working the way it did in this particular manner, prior to this latest version update.

Thanks.

The Sync version present in Firefox 34 uses the password manager to store the passwords. The chrome://FirefoxAccounts entry in the password manager stores the authentication data (kA and kB) in JSON format. The previous version stored this data in the signedInUser.json file in the profile folder, but the current version only stores the sessionToken and needs the password manager for the password.

I've noticed though that if you disconnect from Sync that this also removes a stored password for accounts.firefox.com in addition of the chrome://FirefoxAccounts entry.