Hi gohan, unfortunately I have, I'm doing this procedure:

https://forum.mysensors.org/topic/2437/step-by-step-procedure-to-connect-the-nrf24l01-to-the-gpio-pins-and-use-the-raspberry-as-a-serial-gateway-mysensors-1-x/2

I had already change this number, and this issue continues. This virtual USB port was created here:

sudo ln -s /dev/ttyMySensorsGateway /dev/ttyUSB20

Someone have this erro msg at Domoticz LOG web page?

The sequence is:

2017-07-05 11:04:57.436 Error: MySensors: Error opening serial port!
2017-07-05 11:04:58.436 MySensors: retrying in 30 seconds...
2017-07-05 11:05:27.438 MySensors: Using serial port: /dev/ttyUSB20
2017-07-05 11:05:27.439 Error: MySensors: Error opening serial port!
2017-07-05 11:05:28.439 MySensors: retrying in 30 seconds...
2017-07-05 11:05:57.441 MySensors: Using serial port: /dev/ttyUSB20
2017-07-05 11:05:57.441 Error: MySensors: Error opening serial port!
2017-07-05 11:05:58.442 MySensors: retrying in 30 seconds...
2017-07-05 11:06:27.444 MySensors: Using serial port: /dev/ttyUSB20
2017-07-05 11:06:27.444 Error: MySensors: Error opening serial port!
2017-07-05 11:06:28.444 MySensors: retrying in 30 seconds...
2017-07-05 11:06:57.447 MySensors: Using serial port: /dev/ttyUSB20
2017-07-05 11:06:57.447 Error: MySensors: Error opening serial port!
2017-07-05 11:06:58.447 MySensors: retrying in 30 seconds...

My NRF24L01 is powered supply by an external source.

All the above steps were OK, I did 3 times from the start!