In Terraform after adding the following NSG Rule, I still get an error message below, What could be the issue?

   resource "azurerm_network_security_rule" "someresource_nsg_rule_inbound" {
   name                        ="Management_Endpoint_for_Azure_Portal_and_Powershell"
   priority                    = 110
   direction                   = "Inbound"
   access                      = "Allow"
   protocol                    = "Tcp"
   source_port_range           = "*"
   destination_port_range      = "3443"
   source_address_prefix       = "ApiManagement"
   destination_address_prefix  = "VirtualNetwork"
   resource_group_name         = azurerm_resource_group.someresource_rg.name
   network_security_group_name = azurerm_network_security_group.someresource_nsg.name
   }
    
   ------
 
   │ Error: retrieving Policy for Service (Subscription: "xxxxxxxxxx"
   │ Resource Group Name: "SomeResource-Dev"
   │ Service Name: "someResource-dev-apim"): unexpected status 422 (422 Unprocessable 
    Entity) with error: ManagementApiRequestFailed: Failed to connect to management 
    endpoint someResource-dev-apim.management.azure-api.net:3443 for a service 
    deployed in a Virtual Network. Make sure to follow guidance at 
    https://aka.ms/apim-vnet-common-issues for Inbound connectivity to Management 
    endpoint. Check 'ApiManagement 
    Control Plane - inbound' connectivity at https://aka.ms/apimnetworkstatus.