We’ve investigated diagnostics associated with your account for both RoonServer and the iPad Air. The iPad appears to be relying on a different subnetwork than all your other devices. Is this device using a separate router or access point than your RoonServer machine? Do you use a VPN on this iPad?
Please restart your RoonServer machine and the iPad for due diligence. We’ll watch for your response.
In addition to @connors questions, do you have a separate IoT WiFi network with a (different) VLan ID set?
You say you have a TpLink Router and a modem supplied by Spectrum. Does this ‘modem’ also provide Wifi (there can be a confusion between modems and routers - True modems don’t provide wifi but routers with a built in modem can and usually do)? If so, have you turned off the WiFi on the Spectrum ‘modem’.
If your Roon Server, and your endpoints and clients etc are all connected to the TpLink (either directly or via the netgear switch but the iPad is using a wifi connection to the Spectrum modem, then it will be on a different subnet. If you disable the WiFi on the spectrum modem and connect the iPad to the WiFi from the TpLink router, this will be resolved.