Hi Steve March ,
You don't have sufficient permissions. This operation can only be performed by a manager of the group.
This issue occurs if you're not a manager of the group. In this situation, you're not listed in the ManagedBy attribute.
You must be an Exchange Online administrator, , or a member of the Security Group Creation and Membership role in the Exchange admin center to perform this procedure.
For this issue, you can refer to the following two solutions:
1.Add this script as this group manager:
Set-DistributionGroup <NameOfGroup> -ManagedBy "Admin@contoso.com" -BypassSecurityGroupManagerCheck
2.Use the Add-DistributionGroupMember / remove-DistributionGroupMember cmdlet together with the BypassSecurityGroupManagerCheck parameter to allow users who are not group owners to modify or delete the group.
For more information about this error, please refer to this link:
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