Plug too far away from the Smappee monitor? Try again with your Comfort Plug, close to your Smappee monitor, to be sure that the Radio range in 433 MHz is not the issue.
The Plug could also be too close to the Smappee monitor. The distance should be minimum 1 meter.
Your phone/tablet and your Smappee monitor should both be connected to the Wi-Fi network. The Smappee app on your smartphone communicates with the Smappee monitor via Wi-Fi over the cloud and instructs your Smappee monitor to send out the "Pair with me" command. So an internet connection is also needed!
Remember, the Comfort Plug does not communicate over Wi-Fi nor Bluetooth! It uses a dedicated radio on the 433 MHz frequency. The radio to communicate with your Comfort Plug is built into the Smappee monitor.
The Comfort Plug only works with a Smappee Infinity setup including a Genius as gateway and with Smappee legacy monitors (Smappee Energy, Solar, Plus and Pro). Not compatible with the Connect series.