Also, if it was not clear when @bobbyD said that you did not need to enable wifi to discover wifi devices, you also should not have the hub connected by both wifi and cable at the same time. That can cause weird issues.
Either Cable OR wifi, not both.
Thanks. Hubatit Support said they found it is their problem and they are working on it.
Just to be clear, the problem they identified is distinct from the issue tray_e mentioned above -- that's something you'll want to address regardless if it is a (non-recommended) configuration you ended up applying to the hub as part of your troubleshooting.
I got that. Thank you. I am back to my ethernet only connection.
Quick update - we narrowed down the issue, and working on a solution. Meanwhile there is a workaround for those who are trying to enable Alexa Skill for the first time. Following this document, after successfully completing the linking process and Alexa is attempting to discover new devices, exit the Hubitat Skill in the Alexa app, then go to Hubitat web interface. Locate the Alexa Echo Skill under Integrations tab, and select the devices you'd like to add to Alexa, then click Done. Allow a few minutes for the devices to be added in Alexa app.