Audio zone Devialet 220 disappears

I run Roon 1.3 on a mac mini (late 2012) with OS Sierra.
Directly connected to a Devialet with ethernet cable, Roon randomly sees the audiozone one day, but disappears the other. When it plays its stable.
But when I restart Roon or the mac, it’s always the question if the zone appears.

How to fix this?

How do you connect the Mac mini to the Devialet?

ethernet cable directly into each other