Power cycle the whole network of devices starting from the router, including network switches, WiFi access points, Lumin, and Roon Server, iPad iPhone and Android phones.
Make sure Lumin app setting Roon Ready is enabled.
In Roon settings Audio, find D2 and assign it a zone name.
If you cannot see the D2 in Roon settings Audio, state your brand and model of router, network switches, access points, mesh, and how everything are connected together. Note that if you have a primary router plus a mesh, that usually won't work.