Usage said

When I open firefox I have to sign in and sync every time with newest update.

Try to make new profile via `about:profiles` and set it to default. If its working, export your bookmarks from the old profile and import them to the new profile.

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.

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.