I'm having the exact same issue.Also using Firefox. Asus laptop
Also....
When signing in, if I go to the “Existing User? Sign In” button in the top right-hand corner, 9 times out of 10, it tells me...
“Oops!
Something went wrong. Please try again”
....and I have to hit the “Existing User? Sign In” button in THAT new window and fill in username and password again in order to log in. It's just frustrating at times to have to log in twice when it's the exact same thing that was entered the first time!