vmWare vCenter Server - permissions

What is your defaultResourceGroup token set to (if anything)? You can check it for the dashboard itself in the upper-right down arrow > Manage. It will have a section for tokens. You would want it to point to be your customer folder (from the resource page), and at the dashboard group level and let it be inherited by the customer dashboard(s).

Tokens are like variables/properties that you can assign to the dashboard or dashboard group letting you more easily template dashboards, cloning them across multiple customers for example.

https://www.logicmonitor.com/support/dashboards-and-widgets/managing-dashboards/how-are-dashboards-created#tokens