Why does my GraphQL call using the HTTP client return null? [closed]

I am trying to call my GraphQL API using the generic HTTP client in .NET Core. The query doesn't work when I use the HTTP client. I have this set up in Bruno and get results back.

var queryObject = new
{
variables = new { },
query = $@"orders(take:1 skip:0 filter:""orderNumber == {orderUpdate.OrderNumber}"")     {{
    items {{
        orderDate
        orderNumber
            items {{
                itemNumber
            }}
        }}
    }}"
};

var response = await m_Client.Post<GraphQLResult>(
m_GraphQlSettings.OrdersEndpoint,
bodyContent: JsonSerializer.Serialize(queryObject));

if(!response.Success)
{
    m_Logger.LogError("GraphQL Errors");
    return null;
}

My class:

public class GraphQLResult
{
   public Order? Data { get; set; }
}

public class Order
{
    public OrderHeader Orders { get; set; } = null!;
}

The API returns null and nothing gets run when the request has been sent so it has to do with the query.