The Ayre Codex is not a Roon Endpoint. If it is connected to the Roon Core directly by USB cable it will operate, but otherwise you need something like the microrendu as an endpoint that Roon will recognize on the network. You would connect the Codex to it and and choose the MicroRendu as the zone in Roon. I did the same operation with a Logitech Touch as the endpoint and connected the Codex to the the Logitech via USB. I now use a QX5 as a direct Roon Endpoint using an ethernet connection.
Sonore Microrendu USB to Ayre Codex
Roon bridge running on an iMac sends files to my Ayre QX-5 Twenty digital hub, but Roon core running 24/7 on a Mac Mini tells me to select a zone and doesn't find the Ayre Codex. When I go to the Roon endpoint table only the QX-5 and QX-8 are shown for Ayre. The MicroRendu is shown for Sonore. If I insert a MicroRendu between the Mini and the Codex is that likely to fix the problem? I assume I could select the MicroRendu and Roon would find it.