rs485 to usb converter and libmbus?

[triptec]

So I got a EM340-M1 and one of those rs485 to usb
.
Thought it was a modbus output but then realized it was a mbus and that that’s not the same thing. So I’ve tried to do connect the two but I’ve had no success with either mbsheet or libmbus so I’m wondering if it should work or if I need some other dongle like rs232 to usb or something? I tried to connect the mbus positive to B and the negative to A and also switched them. Scanned for primary and secondary. Is there something I can measure with a multimeter like should there be any voltage between the positive and negative going out or is the any other thing I can/should check?

Thanks