Thats not what it means. I suspect you could de-register the ATV from your account and unplug it, and the error would be the same. The error is just a dumbed down apple error message to account for the most likely issue of the bridge not being discovered. The ATV is NOT a bridge, it acts a Home Hub (which is optional). The only Bridge is the HE Hub.
Did you try this?
Sorry to hear about the frustrating experience you're having trying to get Apple HomeKit up and running. Not sure if any of this will help or not, but I'll give you my high level process for setting up HomeKit. (NOTE: Read the very last paragraph before attempting this process!)
In fact, you should be able to actually Scan the Hubitat Hub QR code BEFORE you add the AppleTV as a "Home Hub" to the system. The Home Hub is NOT required to add an accessory, IIRC. It is only needed to run HomeKit automations and to allow for remote access when away from home. Thus, try adding Hubitat first to see if you get the exact same message about connecting the device to your home network. If so, you will at least know 100% that it has nothing to do with the AppleTV. Another thing to try is turning off your cellular data connection, to force your iPhone to use your home WiFi network. If the iPhone is not using your home network for some reason, then it will never be able to 'see' the Hubitat hub.
I hadn't, I was trying to figure out how to do it with the power supply issues (Hence why I'm using POE. I just figured it out, and no, still won't connect, still same error about making sure the ethernet cable is connected.
A few more things to check...
If your Subnet Mask is anything other than 255.255.255.0, that could explain the issue. Hubitat is expecting 255.255.255.0 as the subnet mask. If your router's DHCP server is serving up a larger network space, then it might cause issues with the two devices communicating.
Yes, signed in with the same Apple ID, as a matter of fact, I used the same phone to initially set it up.
Is this under AirPlay and Home Kit (the only mention of home in the settings)? This is not even an option in my settings. Just setting up a room, with No mention of HUB at all.
You could try hitting the HK port from a command line / terminal windows on your PC
Just fill in for your Hubs IP:
curl -v http://192.168.X.X:21063/accessories
This thread he is using a Linux command prompt with an additional command but I tested with just the curl from windows and it worked on my Homebridge setup, should work on HE:HK also.
Here is my output:
You can check if the ATV is a home Hub under:
Home App > ... menu > Home Settings > Home Hubs and Bridges
But, you do not even need to have a Home Hub to add the HE bridge to Apple Home. You only need the home hub for more reliable control and remote (outside of LAN) control.
Ahh, you're correct. Looks like Apple removed this option with the "New Home Architecture". I just upgraded my Apple Home to the new architecture a few days ago, and now the option to choose whether or not the device can be a "Home Hub" has disappeared from my AppleTV devices.
Here is what I got
Home Hubs and Bridges are not even an option, and setting it as a hub in the Settings on the ATV is also not an option. I'm starting to think maybe Apple made a change they didn't tell anyone about.
Well, at least I don't feel like I am totally insane!!
Are you saying that you don’t even see this section on your iPhone, in the Apple Home app’s Settings?
Going back to the above set of questions... We now know your Hubitat hub is using 192.168.50.220 for its IP address on your home network (from your curl output above.)
What is your iPhone using for its IP address on your home WiFi?
I suspect the ATV has not registered itself as a Home Hub yet because you have no bridge devices, and thus no devices to control and no need for a Home Hub.
I am currently figuring out a way to scan the LAN for the mDNS packets, so you can verify the Hub is broadcasting them.
Is you PC on the same Wifi as your mobile? That would be the best way to test it.
According to my router and phone 192.168.50.21. ATV is 192.168.50.170
The subnet on all three is 255.255.255.0.
I'm getting to a point where I need to get some sleep before I go to work tonight. I'm going to have to dig into this a bit deeper tomorrow.
Isn't that a bit of a catch-22, can't add the bridge to begin with?
Yes. Everything is on the same Wi-Fi or connected via the POE switch to the same router. The PC Is on the Wi-Fi.
Found something to check for the mDNS: zeroconfServiceBrowser | Tobias Erichsen
I installed this software and fired it up. Straight away it found all sorts of stuff. I added the HK app to my dev hub and that showed up as well.
Just select the "HAP" service at the top.
You don't need to have a Home Hub in order to add a bridge device. You could deregister the ATV and unplug it, should still be able to add the bridge device.
All it found was a TV , not the Apple TV. 1 of 2 LG's
Went through all the services listed, habitat didn't show in any of them.
It should find the Hubitat HK bridge, like as I have shown. Also it did find my HomePod as well, so it should probably be able to see your ATV.
Definitely pointing to some sort of networking problem IMO.
You could try clicking the "Restart Integration" link at the bottom of the HK app in HE, while that tool is running. If it still doesn't show up then 
EDIT: Just realized my image above is showing my Homebridge Hubitat integration. Here is my actual HE Hub integration I just setup:
You can see the port is the same one we queried before. And you can reach that port, but if the mDNS is not being discovered then somehow JUST that is being blocked (or not forwarded by the router). I can dig around and see if I find anything on the ASUS side that could be causing it (while you sleep).
Download the Hubitat app
