All my tasks and lists have disappeared, not accidentally deleted

Because your Microsoft To Do lists disappeared on both your phone and laptop, while new tasks still work, this may be an account synchronisation or server-side issue rather than accidental deletion.

The most important thing: don't sign out, reinstall the app, or make further changes to old lists yet. Protect what remains while you investigate.

What to do next

Check the web version: Visit

Microsoft To Do and sign in with the exact same Microsoft account. See whether your old lists appear there.

Check Outlook Tasks: Visit

Outlook on the web and check whether your tasks are still present.

Verify the account: Make sure both devices and the web app use the same Microsoft account.

Contact Microsoft Support: Visit

Microsoft Support and request escalation to the Microsoft To Do team. Explain that years of lists disappeared across multiple synced devices.

Ask support specifically to investigate server-side task data loss and possible recovery, rather than sending you general troubleshooting articles. Don't assume OneDrive can restore To Do lists; they may not be stored there as ordinary files.