Im finding the whole app experience really woeful and frustrating! Had exactly the same experience as you and now can’t set myself as a key user due to this connection issue. Yesterday I had a call to say they are moving it to a different solution/infrastructure to make it more robust and hope to have done so within a week or so, so fingers crossed. At the moment it’s just working for me which makes monitoring charging impossible.I've had same issues too. Kind of worked when I first set it up but I got an error message on the App (saying it wasn't connected) when it clear was. I also couldn't connect via Apple Watch even though the app on my iPhone sort of worked.
I deleted myself off as the key user and tried to re-add myself but I just get a connection error message. Wish I hadn't bothered as it did sort of work before. Now I've got nothing ☹
I have raised a call with Audi who used a cool website to access camera on my phone and lowed me to show them. No feedback yet after 5 days .....The agent did say they have had a lot of calls about this. I'll update if it gets resolved. V annoying!!
All working for me now, but I still get a message about linking vehicle for infotainment system, don’t think I’ll ever get rid of that<rushing outside to try>...
And the apple watch is fixed too. Many thanks for posting!