This is the debugger output:
-[NSFileManager URLForUbiquityContainerIdentifier:]: An error occurred while getting ubiquity container URL: Error Domain=LibrarianErrorDomain Code=11 "The operation couldn’t be completed. (LibrarianErrorDomain error 11 - The requested container identifier is not permitted by the client's com.apple.developer.ubiquity-container-identifiers entitlement.)" UserInfo=0x28a970 {NSDescription=The requested container identifier is not permitted by the client's com.apple.developer.ubiquity-container-identifiers entitlement.}
Setting the app identifier as com.companyname