APC220a Configuring but not transmitting

Hey, I have 2 APC220a wireless transceiver modules (https://www.robotshop.com/media/files/PDF/dfrobot-apc220-manual.pdf) which I've managed to configure (1200 baud rate, 450MHz frequency, different NODE ID's for each transceiver), however, I can't manage to receive or transmit a signal.

I have each transceiver connected to my PC via GND, VCC, TX and RX using a TTL-UART converter, however, when I open the com port for each transceiver (Com2 and Com3) set to 1200 baud rate, I can't manage to receive any signals.

Does anyone have any idea what the problem might be?