I didn't have to log out of iCloud or uninstall any Home app on iPhone/iPad. Below more simple solution actually worked for me, too:
"I had the same issue. My wife could receive the invite but could not join. Nothing happened after accepting. Her phone was updated after switching to the new Home architecture. I thought nothing worked until I did this:
(I was able to delete my wife from homekit users on my admin phone)
- turn off all iphones
- unplug all hubs (reboot is not sufficient)
- wait couple of minutes
- plug in all hubs
- start up iphones
- the wife was instantly able to access our home again
Hope this helps someone."
source:
https://discussions.apple.com/thread/254464994?page=2
So I also turned off all iPhones, MacBooks, Apple Watches, iPads etc. Then pulled plug of all hubs (HomePod mini and AppleTV), waited for 10 min, then step by step plugged each hub in individually, starting with AppleTV (main hub), then after it was online again I proceeded with first HomePod mini #1 and only after that with HomePod mini #2. Only then first my iPhone (I am the home admin) and then partner iPhone. I was then able to delete partner from Home and send a re-invite. Only after accepting it on the partner iPhone and going through all prompts there, after checking if everything was back, I then turned on the other devices again.
Remark: On all iPhones, I closed Home apps before turning them off. In addition, on partner phone, before all of that, I deleted the "standard" home that gets created by apple after first opening the home app, and directly closed the app afterwards before a new one was created.
Hope this helps!