Internal Server Error when creating private endpoint with Azure provider

Hey, when i tried to create private endpoint with Azure provider i got error.

this is the tfvars file:

"pep-child-growth-dev-westeu-006" = {
    useKey                          = false
    application                     = "child-growth"
    env                             = "dev"
    pepIndex                        = "006"
    region                          = "westeu"
    rg_name                         = "rg-child-growth-dev-westeu-001"
    linked_resource                 = "cosmos_postgres"
    linked_resource_name            = "cosmos-child-growth-devwesteu-001"
    hasNic                          = false
    custom_network_interface_name   = "pep-child-growth-dev-westeu-006-nic"
    private_service_connection_name = "pep-child-growth-dev-westeu-006"
    private_dns_zone_group_id       = "xxxxxxxxxxxxxxxxxxxxxxxxxxxx"
    private_dns_zone_group_name     = "default"
    private_dns_zone_ids = [
      "xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx"
    ]
    subresource_names = [
      "postgresqlServer"
    ]

    subnet_name = "snet-cosmos-002"
    tags = ({
      "Application" : "child-growth",
      "Subscription" : "child-growth-dev",
      "Environment" : "Dev"
    })
  }
}

this is the error:

Error: creating Private Endpoint "pep-child-growth-dev-westeu-006" (Resource Group "rg-child-growth-dev-westeu-001"): network.PrivateEndpointsClient#CreateOrUpdate: Failure sending request: StatusCode=400 -- Original Error: Code="InternalServerError" Message="An error occurred." Details=[]

any ideas? thanks!