Your session is tied to the open tab for security reasons: closing the tab or the browser ends it, so you have to Sign in again when you come back.
This is deliberate, not a fault. Your sign-in details are held only in the tab you are working in and are never kept on the device, so nothing is left behind on a shared or public computer.
What that means day to day:
- As long as you stay in the same tab, the session renews itself — you will not be dropped in the middle of a long piece of work.
- Open a new tab and it will not recognise you; it asks you to sign in too. Following links in the tab you already use is smoother.
- Close the tab and return later, and you enter your email and password again.
The Remember me on this device checkbox on the sign-in screen does not extend your session today. Ticking it will not keep you signed in after the tab closes, and it does not change how long a session lasts.
If your password is rejected or your account is locked, that is not about session length — it is a separate sign-in problem.
Also asked as: Why do I keep getting logged out? · Does "Remember me" actually work? · Closing the browser signs me out, is that normal? · Why does every new tab ask me to sign in again?