Not able to read response from device on USB

I have a device I can communicate to via USB/RS232 port.
I know it receive the command I send because it react to them.
I have a command to retrieve its state that should respond but I'm not able to read any response ! What's wrong in my flow ?
I know that command works otherwise because I've tested it from a terminal.

here is the link to the protocol of the device :
https://www.dropbox.com/s/xbjc8xzbd25cm9d/Sumry6kW%20inverterRS232%20Protocol.pdf?dl=0

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According to the docs each command should be followed by a carriage return \r or possible \r\n. So C\r would be On

The C command is the start command and that one works perfectly

The one I can't get a response from is the "Q1" command that is made the same as the C or the S0R0000 commands.