I've lost my Recovery Key

If you don't have a copy of your Recovery Key saved anywhere, or another computer or mobile device that's synced (see Where can I find my Recovery Key?), you can generate a new one.

Warning: This will erase all of your data stored on the server. New data will be secured by this key and then uploaded. Your other devices will stop syncing, unless you update them with the new Recovery Key. At the top of the Firefox window, click on the Firefox button and then select Options Click on the Sync panel. Click Set up Firefox Sync and a new window will open. Under I already have a Firefox Sync account, click Connect. Click I don't have the device with me. Enter your account email address and password. Click I have lost my other device and a new Recovery Key will be made for you. Tip: It's a good idea to print or save your Recovery Key so that you can access your information even when you are away from this computer. Then click Change Recovery Key. You will see the Setup Complete screen. Click Finish to close the setup window.

I’ve forgotten my Sync password — how do I reset it?

To get a new password follow these steps.

Warning: Your other devices will stop syncing unless you update them with the new password. Go to https://account.services.mozilla.com. Click Forget your password?. Enter your username (this is the email address you used when you created your Sync account) and fill in the captcha to prove that you're a real person. Click Email Reset Key. You will receive an email with a link. Open the email, click the link and a new page will be opened. Type your new password twice. Click Change My Password to save it. Now you're ready to go. Remember to update your password on all your synced devices by clicking Sync Now and Preferences... in the bottom error bar that will be displayed.

I've forgotten my master Firefox password

For security reasons, your master Firefox password is not synced. If you've forgotten your master password and want to stay synced, you'll need to reset your master password and re-add your computer to Firefox Sync.

Warning: This will clear your usernames and passwords stored on your device and disconnect you from Firefox Sync. However, your usernames and passwords on the Sync server won't be cleared. Reset your master password by following the instructions in Reset your Master Password if you've forgotten it. At the top of the Firefox window, click on the Firefox button and then select Exit Start Firefox. Re-add your computer to Firefox Sync

As i dunno your case i have given all the 3 cases please try them.

Do you see the correct user name and password and Sync key in the Password Manager?

You can find the sync account password and the sync (recovery) key in the password manager on computers where a sync account with a specific e-mail address has been set up.

• Firefox/Tools > Options > Security: Passwords: "Saved Passwords" > "Show Passwords"

Look for:

• chrome://weave (Mozilla Services Password)
• chrome://weave (Mozilla Services Encryption Passphrase)

You can also try to see if you can login here:

• https://services.mozilla.com/ Firefox Sync » Home
• https://account.services.mozilla.com/