The same happened to me. Looking at the code the app while pairing is looking for PowerTags already paired on the gateway with IDs between 150-169 (I guess). Simply scanning modbus slaves, it should work with a PASx00 gateway. I tried using a PAS600 with powertags paired and set to those IDs but no success. The app appears to be broken. I now use the PAS600 (PAS400 should work also) and the Homey app for Modbus TCP/IP. I use advanced flows to read the data and transfer it to Virtual Devices (Virtual Device App) with Voltage, Current, Power, Energy capabilities enabled. It works and should work with Acti9 Smartlink, just get the PowerTags id right. (I added a scale card but found it’s not needed, you can connect the output from the modbus card directly to the Virtual device.)
