Hi @Stu Haynes
Are you sharing files with this user in a private chat or in a team channel?
Can you provide details or screenshots? (Please note that personal privacy information is covered)
As far as I know, you can't share files with external users in Teams. If you're in a Teams channel, external users can only contribute to the shared channel.
For more information about external access, please refer to:
https://learn.microsoft.com/en-us/microsoftteams/communicate-with-users-from-other-organizations
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