OneDrive is not found. Message attachment can't be migrated (4379368)

Customer is getting error 'OneDrive is not found. Message attachment can't be migrated' when running Chats migration.

The error means that a file shared in a chat was not migrated to the target tenant as part of the OneDrive migration for the owner - that is, the person who originally shared the file.

As a result, when the chat migration process attempts to update the link to that file, there is no corresponding file in the target environment to link to.

This is expected behaviour if the user who shared the file is outside the migration scope, or if the file was deleted by the owner or another party before the migration took place.

It could either files that have not been migrated yet or one will not be migrated. 

This typically occurs when a domain has been moved, and the user's OneDrive has not yet been fully updated or made available via Graph API. While OneDrive might still be accessible through the UI, if it hasn't propagated through Graph API, the tool cannot retrieve the necessary data, which results in the errors you're seeing.

During a cutover migration of chats, encountering errors where OneDrive attachments are not found can disrupt the process. To avoid this, it’s crucial to ensure all preliminary steps have been properly completed before running the chat migration task.

Resolution 1:

1. Start by verifying that a "Discover All" task has been run after moving the domain from the source tenant to the target tenant. This step ensures that all user and data mappings are properly refreshed.
2. Next, check the permissions of the migration account to confirm it has the required access to OneDrive data, including the ability to read and migrate files. Also, make sure your migration settings are configured to include both chat content and attachment.
3. Additionally, double-check the source data to confirm that the OneDrive attachments linked to chat messages still exist and are accessible.
4. Finally, running pre-migration checks can help identify potential issues or missing data before proceeding, minimizing the risk of errors during migration.

Resolution 2:

1. Sign in to https://developer.microsoft.com/en-us/graph/graph-explorer with the errored user profile.
2. Put the ObjectIDof the user and run this query: https://graph.microsoft.com/v1.0/{ObjectID}/drive
3. If the results return 404 error, it's Microsoft related issue. 
4. If the results return value, then create a new task and it should run successfully.