There are a couple of things to try here, in case you have not already:

NOTE: TPControl must be running and have full application focus on your device, in order for TPTransfer to locate it.

- Ensure that your computers relevant network adapter has been selected in "TPTransfer -> Tools -> Settings -> Network" i.e. there should be a "tick" icon next to the adapter

- Ensure that any software Firewall running has Port 10700 enabled 

- Try manually adding the IP address of the device that you are trying to locate, by using the "TPTransfer -> Add Device" option

- Try removing all devices currently in the Device list for TPTransfer by selecting the "X" next to each device and, then close and restart TPTransfer

- Disable the "Automatic Device Polling" option in "TPTransfer -> Tools -> Settings -> Network"

If you are still experiencing trouble, try the following: go to 'TPTransfer -> Tools -> Settings -> Diagnostic' and enter the IP address of your TPControl device in the "Network Address" field. Perform a 'Ping device' test, followed by 'TCP' and 'UDP' tests. Both the TCP and UDP tests must pass in order for TPTransfer to communicate successfully with TPControl.

If you have access to the "TPC User ID" account that the token for the device is registered to, you can also use TPCloud and the "TPCloud update" feature to transfer the TP4 file to the device (provided it has access to the internet).