Lyngdorf TDAI 2200 Master/Slave

I have 3 Lyngdorf TDAI 2200 amplifiers that I would like to be connected.

As a start, I connected 2 of them.

#1 is set to Master, Address 1, and 57600 Baud rate.
#2 is set to Slave, Address 2, and 57600 Baud rate.

They are connected via RJ12, AUS`X on Master, to Input on slave.

It does not work….have I forgotten something?