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 Reseller permissions or refused the partner relationships agreement.
Take Microsoft Reseller access credentials from the corresponding Office 365 application instance and check with Microsoft Support why permissions were revoked.