to remove a user from the resticted section on Office 365 please folloow the below steps,
1. log into the Office 365 portal.
2. Click on the waffle to access additional settings and log into the Security admin center.
3. in the Microsoft Defender admin page under the additional settings go to Email & Collaboration, and click Review
4. Click on the Restricted Entities option,
5. Users will be listed, and can be removed from the list here, please note that the release takes up to 48 hours as the process is solely managed by Microsoft and their internal process.
For further information please feel free to contact me if any of these steps are unclear.