Sodaq Mbili / Lopy Pycom Serial communication

Hello to all,
I am trying at the moment to make a serial communication between my Arduino Sodaq Mbili and a Lopy from Pycom.
I found a cable that allows me at the same time to have serial connection between my Sodaq Mbili and my Pycom, and also a connection to power source. I first downloaded on my Pycom a code in which i create an uart connection at 115200 baudrate, and then send “Hello Arduino” through this uart connection.

I then downloaded on my Sodaq another code in which i created as well an uart connection at 115200 and then the board waits for incoming data using Serial.available().

Both work separatly. In order to test my connection without using my computer, i inserted an SD card in my arduino so that the data received on the SODAQ gets stored onto the SD card. And then i just plug the first two cables to my Sodaq and Pycom then i plug the last cable to a power source (which is not my computer).

The thing is…nothing gets stored on the SD card. I wanted to know, via the image I sent, if you think everything is ok, or if I could be missing something.

Thank you for you reply once again.
Yours sincerely,