Same here - I have a CoreData with CloudKit integration, everything worked on previous version and after installing XCode 13.0 beta 4 yesterday - not working anymore and failing with error:
error: CoreData+CloudKit: -[PFCloudKitSetupAssistant _checkUserIdentity:](1217): <PFCloudKitSetupAssistant: 0x60000217db00>: Identity fetch failed with unknown error: <CKError 0x600000bcd2f0: "Account Temporarily Unavailable" (1028/2011); "Account temporarily unavailable due to bad or missing auth token">
Resetting (clear) simulator etc does not seem to help.