Lora rak811 con Raspberry PI 3

Good morning,

I am working with the rak811 and I followed the next tutorial provided by rackwireless, every step has worked excellent until the test which command is “at+send=lora:2:123456” however when I tried to connect the rak with another device how raspberry Pi 3 (with Python 3 code) it does’t work. The issue is the port which does not work in the stipulate time, in another words, my code run but appear a problem with the serial port “rak811.serial.Rak811TimeoutError: Timeout while waiting for response”
Do you know which could the problem be?