I was getting 401 errors yesterday with beta 2. Today, with beta 3 I am getting the following error:
Error Domain=AMSErrorDomain Code=12 "Mescal Failed" UserInfo={NSLocalizedDescription=Mescal Failed, NSLocalizedFailureReason=SAPInit failed: -42049}
The WeatherKit Capability and App Service have been added to the Identifier, as well as adding the Capability in Xcode, so I believe it should be all set as far as that goes.