Sign-in sessions do not last forever. Clearing your browser data, using a private window, or changing your password on another device will also end a session.
Tick Remember me when you sign in to stay signed in for longer on that device.
The usual causes
- The session simply expired.
- You cleared your browser data or cookies.
- You were in a private window, which forgets everything on close.
- You changed your password on another device.
Staying signed in longer
Tick Remember me when you sign in. On a shared computer, do not — and sign out deliberately when you finish.