According to your case description, you should contact your organization administrator or plan owner and ask them to add members in the Microsoft 365 group in the admin center. Then add you back to the new plan member list.
Add a member to a group in the admin center
- In the admin center, go to the Active groups page.
- Click a group name.
- In the details pane, on the Membership tab, select Members, and then select Add members.
- Search for or select the name of the member you want to add.
- Select Save.
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