A cloud-based task management app from Microsoft that helps users organize and manage daily tasks across devices.
For Microsoft To Do, this error usually occurs in these supported cases:
- The list was deleted before the recipient joined it. In that case, the recipient will see a message telling them to contact the person who shared the list.
- The list owner uses a work or school account, and the invited user is outside that same work or education organization. Microsoft To Do list sharing for work or school accounts is supported only between accounts within the same place of work or education.
- The invited person does not connect with a Microsoft account when using a shared list link. For shared task lists, only people who have a Microsoft account can connect to the shared list.
- There may be an ongoing service issue. A documented Microsoft Q&A case reports the same “can’t join list / list isn’t available” behavior as part of an ongoing incident, with admins able to review details in the Microsoft 365 Admin Center under issue ID MO1213801.
Recommended checks:
- Confirm the list still exists and is still being shared.
- In To Do in Outlook on the web or Outlook.com, right-click the task list.
- Select Sharing options.
- If needed, create a fresh invitation link.
- Verify the recipients are using supported account types.
- If the list owner is using a work or school account, recipients must be in the same organization.
- If sharing more broadly, recipients must sign in with a Microsoft account to connect to the shared list.
- If all tested accounts fail, ask the Microsoft 365 admin to check the Microsoft 365 Admin Center for a current service incident affecting Microsoft To Do sharing, including MO1213801.
If the invited users are outside the organization of a work or school account owner, that sharing scenario is not supported in Microsoft To Do.
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