E32 Lora Library Example Not Working?

Hi, I would like to ask about the issue I have with the E32 Lora library example. In my set-up I use two esp8266s, and 4.7k resistors for the serial connections. I also followed this website's tutorial for the set up. I did not connect the AUX pin. The issue is, when I use the example sendFixedTransmission and receiveFixedTransmission examples, I was able to get the word "Success" in both of the serial monitors but there is no transmission. Sometimes, there was only an inverted ? in the receiveFixedTransimission serial monitor after the line "Success". What did I do wrong? I also used the transparent transmission example, but there is still no transmission. Please help :(.