Some Azure resources differentiate RBAC roles between the control plane and the data plane.
Whilst you have significant privileges on the Control plane, you need to be assigned them explicitly on the data plane. Assuming that you have selected the model of Azure RBAC for Kubernetes Authorization; The role you should assign is the Azure Kubernetes Service RBAC Admin.
Other services like Key Vault (w/ Azure role-based access control) behave in this same way.