Authorization Failed issue

I have a application on asp .net , which i use to get information about my Azure portal , it working well for costing and virtual machine lists etc through api . but when i am getting the reserve instances lists and information APi, it shows me an error : AuthorizationFailed , and the message is : {does not have authorization to perform action 'Microsoft.Capacity/reservationOrders/reservations/read' over scope '/providers/Microsoft.Capacity/reservationOrders} ,  i have provide the administrator/owner role to app