A Microsoft file hosting and synchronization service.
Dear Estelle,
Greetings! Thank you for posting in the Microsoft forum.
This is how sharing with external user works. The Shared with me section in your OneDrive for business will show files/folder only if the user sharing the content is from your own organization.
In case, the content is shared by a user outside your organization, you can gain access from the links in shared email, but the content will not appear in Shared with me section. The same happens with the external user when you share the content from your OneDrive for business. It does not matter whether the external user is using a work or school account or a personal OneDrive account, the reason being you are not from the same tenant and your account exist on different Azure Active directly.
If you need help, let me know. We appreciate your understanding and co-operation. Have a nice day. Stay safe and stay healthy.
Sincerely,
Neha Singh | Microsoft Community Moderator