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Private::Cookie

You may be in Private Browsing mode or told Firefox not to remember.

Type about:preferences#privacy<enter> in the address bar. The button next to History, select Use Custom Settings.

Turn off Always Use Private Browsing Mode Turn on Remember My Browsing And Download History At the bottom of the page, turn on Clear History When Firefox Closes. At the far right, press the Settings button. Turn on ONLY Cache and Form And Search History leaving the others off.

Is the Firefox Password Manager working properly ?

Current Friefox version uses the password manager to store the credentials to connect to the Sync server.
When Firefox is started and you use the master password then you need to enter the master password to be able to connect to Sync.
The chrome://FirefoxAccounts entry in the logins.json file stores the Firefox Sync account authentication data (kA and kB) in JSON format (this entry is hidden from Lockwise, so you need to check logins.json).
The signedInUser.json file in the profile folder stores the sessionToken that is used once you have logged on successfully.

Is the Firefox Password Manager working properly ? Current Friefox version uses the password manager to store the credentials to connect to the Sync server.
When Firefox is started and you use the master password then you need to enter the master password to be able to connect to Sync.
The chrome://FirefoxAccounts entry in the logins.json file stores the Firefox Sync account authentication data (kA and kB) in JSON format (this entry is hidden from Lockwise, so you need to check logins.json).
The signedInUser.json file in the profile folder stores the sessionToken that is used once you have logged on successfully.

No, lockwise automatically flushes out all synced data.

here's what happens everytime I start firefox first time after restart PC: 1. everything is fine for about 60s 2. window suddenly closes and restarts 3. lockwise is cleared and if click the sync button, it asks to re-login

I tried what Fred said and it doesn't work, same as before.

I think this would be the most annoying thing. Could there be an option that firefox not to clear lockwise under any circumstances?

You can create a new profile as a quick test to see if your current profile is causing the problem.

See "Creating a profile":

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

If the new profile works then you can transfer files from a previously used profile to the new profile, but be cautious not to copy corrupted files to avoid carrying over problems.

• https://support.mozilla.org/en-US/kb/recovering-important-data-from-an-old-profile