I'm not sure where your iPad is relative to the router and where you are checking the signal. The inssider values look good, a link score of 100 is ideal. Is the Devialet App you are using on your iPad the volume control, mine works whether I am connected to 2.4GHz or 5GHz on my iPad. My thoughts on 1 were if you had everything running on a wired connection you could then disconnect and switch to a wireless connection to see if it would still work - that would show if it was a WiFi problem or an iPad problem however that won't be practical if it is the iPad App. Are you running your 2.4GHz and 5GHz bands as a single network, or do they have different SSIDs? Have you checked your actual download speed on a wireless connection?
PS I've just come across another possibility - check App remote control is authorized under Remote settings in the Configurator, but if you have had it working that seems unlikely.
PS I've just come across another possibility - check App remote control is authorized under Remote settings in the Configurator, but if you have had it working that seems unlikely.
Roon -> AIR -> Ethernet -> D220-> KEF Reference 3