Home stuck on 'Loading Accessories And Scenes'

First off there seems to be no category for Home so I've just picked iCloud.

So for the second time since I started using it (about 2 years ago) I clicked on 'Home' on my phone this morning and got a blank screen that says 'Loading Accessories And Scenes'. I kill the app and try it again, the same. I hunt around and find a suggestion that involves turning off the keychain, disconnecting Home from iCloud, turning on the keychain and then running it again. After saying to enable iCloud the same message comes up and it waits there.

But there's more... I asked my HomePod to turn on a light and it replied that there 'may be a problem with my iCloud account' so I opened Home on my iMac too and get the same problem.

After hunting around I saw a post that says that you should check your iOS version. It was ok yesterday but I noted 13.5 is out today so I've updated my phone and tried again. Guess what? It's still saying the exact same thing!

As is my iPad. And my wife's iPhone on another account but the same home.

So has anybody else seen this and does anybody have any clues as to the solution? Last time I wound up having to reset it and recreate a LOT of scenes and automations (which it took me weeks to get right) and I really don't want to have to do that again.

So ****** frustrating that there seems to be no way to backup the Home config in a way that you can restore it (as much for when you make a change and break something as for when this sort of thing happens!!!)