What happens in the gui if you try and refresh InternetGatewayDevice.LANDevice.1.WLANConfiguration.1.AssociatedDevice? Do the devices show up?
FYI, there is no need to use wireshark or tcp dump. If you are on a dev server, you can set the cwmp.debug config parameter to true and see the entire soap conversation in the debug file. If you are on a production server, or only want to see one device, create a new config param for cwmp.debug and use this for the value: DeviceID.ID = "<your-acs-id-here>". The location of the file is determined by the GENIEACS_DEBUG_FILE param in the genieacs.env file.