Finally got mine working. I think what got me going was realizing that, on the dev website, where you create the App ID. You have to select WeatherKit in BOTH Capabilities AND App Services. Once I had both of those checked, it still took another 30 mins or so for it to take effect.

Same problem here. I see that a couple of you have said it resolved. What (if anything) did you do? Or is it just that the App ID provisioning is taking a long long time. ???