Trading is disabled means that the broker is not ready to execute the order. We see that trading is not allowed on your slave account or for the given symbol. Please check on your trading account if you can trade manually and contact your broker. With MT4, it could mean that you have connected your Slave account with the investor password instead of the trader password. With LMAX, please verify that you have access to the web API just contact LMAX and ask them to activate the .NET API for this account; they know exactly what they have to do with this request.