Prevent automatic logout.

Since today I am regularly logged out automatically when I have not pressed enter for too long.
That often happens to me when I spend a little longer formulating an reply.

Previously you could check whether you wanted to stay logged in, but I no longer see that check mark.
How can I prevent myself from being logged out automatically when I need a long time formulating an reply?

SOLVED: The checkbox for 'stay logged in' is back.