Communication with 3rd party Modbus TCP/IP device

I have a PXC00-E96.A to communicate a 3rd party power meter through TCP/IP. It have 10 devices at IP gateways ( slave address form 11 to 20).

And the problem is the initial 3 device always no response(). But using the modbus poll software can get the data from the failed device.  Is this the controller problem, or others error?