Chromecast Audio stopped working

[Bill_Janssen (Wigwam wool socks now on asymmetrical isolation feet!)]

Core is a Synology DS918+, DSM 6.2.2-24922 Update 4, Roon 1.7, build 511

Netgear Nighthawk R7000, WiFi stable

Output is Chromecast Audio, firmware 1.42.172094

The problem is that I get the initial “blurp” when I try to play something from Roon, but then nothing. Eventually I get a Roon error on my Control device, saying “Audio device refused to switch input to Roon”.