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
This tutorial helped me solve this error: https://goddess-gate.com/dc2/index.php/post/452
(Be careful with Team-ID and APp-Id , I confused them too in the course of setting up my project)