To setup a group in Multiroom panel:
We suggest to cable via ethernet the Master group device to the router (if it’s not possible use the 5GHz network as preference)
Click on GROUP DEVICES
Click on ADD to add the selected device to the group
Note: no Master group volume control available ; it's not possible to create group between devices on different networks
Your music is not perfectly synchronized?
Go to SOURCES→MULTIROOM→SETTINGS
increase the hardware latency in msec unit, of the relate device
adjust the buffer size in msec unit (in case your hardware/network connection is not performant). This will delay all the network devices