Managing meetings and events using Outlook on the web for business
Dear Cuong Tuan Dinh,
Good day!
Thank you for posting to Microsoft Community. We are happy to assist you!
As per the description you have shared, we understand that your To-Do Tasks are disappearing by themselves.
- May I please confirm if you check your To-Do tasks using different browser? if not, please kindly check your To-do tasks on different browser if you can find your To-Do tasks there.
- You may also log out of your account and clear your browser cache and log in again and check if you can find your To-Do tasks.
If the issue still persists, we do understand your concern here, but since our forum dedicatedly focuses on Microsoft Business Exchange online related scenarios. However, as your concern is related with Microsoft To-Do, we provide some limited knowledge about some aspect of Microsoft To-Do related queries. For Microsoft To-Do, we have a dedicated team with special expertise in Microsoft To-Do queries, so we sincerely recommend that post your concern in our dedicated Microsoft To Do - Microsoft Community Hub for further assist. Hopefully they will give you accurate and efficient solution for your concern.
Thank you for your precious time and understanding. For other concerns, please do not hesitate to add your post in the Microsoft Community Team.
Stay safe and healthy.
Have a nice day!
Sincerely,
Libeamlak | Microsoft Community Moderator