Known Issue: Can't set up Chromecast and Chromecast Audio using Ethernet adapter
The Chromecast team is aware of an issue that prevents some users from setting up their new Chromecast or Chromecast Audio devices using the Ethernet adapter.
Who is affected: Some Chromecast and Chromecast Audio users who are setting up their new devices for the first time using Ethernet adapter.
Workaround: The team is currently working on a fix for the issue. In the meantime, you should be able to use the workaround below: