There are 5 terminals that connect the relay board to the RSIO board. Two of those lines are GND. Use a short jumper wire to connect those two GND terminals together. This enables 2 way communication on the board so it responds to commands sent by Base Station.
If you are not connecting this board to a native RS 232 port on a PC then I recommend moving the on board PC/MAC jumper to the MAC position.
Thank you,
Travis Elliott