Hello Zheng Kon,
Thank you for sharing your concern here in Microsoft Community Forum and we hope that all is well.
Based on the description, the tasks created with due dates within Microsoft Loop does not synch across to Microsoft To Do app. Let us see on what we can do to help address your concern.
Before we proceed any further, we would like to set your proper expectation that Microsoft Loop is still in public preview and users may experience known and new issues. During this preview, we will need your feedback to help us improve your experience.
We would like to ask few questions to help us isolate the issue further.
- How did you create the tasks with due dates in Microsoft Loop? Is it directly through Microsoft Outlook application?
- Are you using personal account or work account for Microsoft Loop?
- Are you using personal account or work account for Microsoft To Do app?
For the meantime, you may check the article below to check known issue for Microsoft Loop. You may also check how to check Loop components on other applications that is currently supported.
We look forward to your response. Kindly let us know, if there is any misunderstanding or clarifications of our description by sending us a reply.
Sincerely,
Tomm_A
Microsoft Community Moderator