Hello.
Very frustrating indeed.
After hours of searching the web for answers to the "invitation failed" issue, I have finally decided to write in this thread to let some steam off.
Still in ios 11.2.2, I managed to invite and connect the wife (after some trouble, but not much). Still, it's seems totally impossible to get an invite through to any of the two kids. They can create a home and send an invite to me, but that will never reach me.
So, I own the home.
Yes, the kids have valid Apple-IDs. (Not xxx@icloud.com, but other email addresses.)
Got latest software on Apple TV.
As suggested in numerous posts, we've logged off/and on iCloud (or Apple-ID as the iPhone calls it). (To be honest I don't know the difference...)
As of today we are on ios 11.2.5. Posts from beta testers implie that now, finally, everything should work. Well, it doesn't.
In many threads I get the impression that people actually succeed in getting everything set up. But each in their very individual way. There's a lot of "log out of EVERY device", "restart this and that", "be sure to activate key ring", "update software", and so on and so on. Testing all tips in every possible order would take hour and hours. I assume Apple did not intend for HomeKit to be so hard to set up.
I'll rest now for a few days to see if someone can come up with a set-up routine that works for everybody.
If not, I can only come to the conclusion that HomeKit is not working, and Apple is not intending to get it to work.
Please forgive my rambling, I've had a bad Apple day.
Anders.