Need to go to Tools -> Login, close browser, then open to restore sessions.
On my Android phone (Nokia 9, FF 68.1.1), I frequently (after a couple of minutes of inactivity) need to do a strange "reset" in order to allow sessions to work properly on websites. It applies to _all_ websites that use some kind of session, my best guess is cookies.
Symptom: website no longer recognizes the session, either asks for a user name and password (and keeps failing), or shows notices of using ad-blockers, showing generic content instead of customized view, etc.
Regain sessions: go to Tools -> Logins (spinner will show, but logins will never appear). Close Firefox. Open Firefox. All pages work again!
- User Agent: Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:69.0) Gecko/20100101 Firefox/69.0