Home sharing works on all Apple TV 4K except the 2nd gen Apple TV 4k

• The Apple TV box must have the matching Apple ID account entered for Home Sharing, in Users and Accounts. Verify that.
• The Apple TV box must connect to the same home network. For Wi-Fi, that means using the same SSID network name. Verify that.

Use Home Sharing to share media from a computer to other devices - Apple Support

Unless someone else chimes in with a good idea, I would suggest to contact an expert from the Apple Support staff for further assistance. Contact Apple for support and service (phone numbers) or start your support request online (chat/​email/​callback).

Thanks for the follow-up. At least you now know where to troubleshoot if you ever want to go wired again.