Grant Purview Export Permission
When exporting the results of a Microsoft Purview Content Search, the user must have the permission. This permission cannot be granted by the same user to which it is being granted.
First, Connect to the Security and Compliance Powershell
Add eDiscovery Manager Role to admin:
Add-RoleGroupMember "eDiscovery Manager" -Member <username>
Promote admin to Case Admin
Add-eDiscoveryCaseAdmin -User <username>
Microsoft Answers: user-with-global-administrator-and-compliance-admi