The "Access Denied." appears on attempt to check a Tenant subscriptions with
Get-MsolSubscription -TenantId 7F7914E0-...-7A0A76BE4C0C Get-MsolSubscription : Access Denied. You do not have permissions to call this cmdlet.
Customer revoked Delegated Admin Permissions (DAP) or canceled Partner Relationship agreement.
Obtain the Microsoft Reseller access credentials from the corresponding Office 365 application instance and check with Microsoft Support why permissions were revoked.