I wired mine exactly as the wiki said too. RESET to D2 and CS to D4, if you do anything different you need to change the init line.

The key lines for me were

#define RX_LEN    11

lora.setPayloadLength(RX_LEN);  

Once I did this it worked, with the tx test  from this page https://wiki.dfrobot.com/FireBeetle_Covers_LoRa_Radio_868MHz_SKU_TEL0125 I could test both (rx and rx)  from GitHub if you think it would help you.

There is an error in the reciever  example code. Try the version in Github instead.

https://github.com/DFRobot/DFRobot_Lora/blob/master/examples/receiveTest/receiveTest.ino