It looks like the only option was to re-install my machine. So a clean windows installation with all the programms including firefox.

It's possible that you have the browser set up to remove cookies when the browser is closed.

Your ‘logged-in’ status is stored in special cookies. If the cookie is removed, you are logged out. +++++++++++++++++++++++++++++++++++++++++ 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 Cache and Form And Search History.

I have done this chanching, i must wait, what my stystem does, after a cold start.

chanching?

dictionary.com No results found for chanching

Are you using an external Password Manager or use cleanup software that might be removing the Sync credentials stored in the Password Manager?

The chrome://FirefoxAccounts entry in the password manager stores the Firefox Sync account authentication data (kA and kB) in JSON format. The signedInUser.json file in the profile folder stores the sessionToken that is used once you have logged on successfully.

FredMcD said

chanching? dictionary.com No results found for chanching

I have done the above adjustments, but I do not know the results yet, because I have not finished the computer yet. Apologies for the error, I'm not very good at writing in English.

cor-el said

Are you using an external Password Manager or use cleanup software that might be removing the Sync credentials stored in the Password Manager? The chrome://FirefoxAccounts entry in the password manager stores the Firefox Sync account authentication data (kA and kB) in JSON format. The signedInUser.json file in the profile folder stores the sessionToken that is used once you have logged on successfully.

I don't use antoher password manager, I use firefox. And I use wise disk cleaner. Now i turn off my pc, and didn't clean with it, to see what the result is, i come back later.

We strongly recommend against using third-party programs to 'clean up' after Firefox because sometimes they remove needed files. Firefox can be set to clean up after closing.

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

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 Cache and Form And Search History.

My reaction is a little late, because I wanted to see how sync work after a few days. But firefox sync has retained my login after the changes made in my settings. And I have not allowed wise disc cleaner to clean anything from firefox anymore. And apparently that worked. So thank you very much for your help. My question is solved.

Glad to help. Safe Surfing.