I logged in today and discovered that all my tasks and projects have disappeared. I access the list on my Windows 7 HP computer.
Please confirm, have you signed in with the same account you normally use? We do have the ability to use Google sign in, which can sometimes create a new account. It's very unlikely that all your data is gone, as we have things in place to prevent this.
If you are signed into the same account, please let us know which of our apps you are using, Windows App, Outlook Plugin, or other? Were all your tasks fairly old, or recently created? And to confirm, you are on the internet and never went offline?