Domain registration order fails with the following error in Provisioning Item view page:
Registering domain in external source failed. An attempt to call external container for name servers failed due to unhandled errors during call. Domain status:Prepared
The first time provisioning failed with another error.
Issue is caused by product bug with id #PBA-63694 ("Domain registration order can not be completed if first request to POA failed").
Issue is fixed in BA 6.0.5. Consider upgrade BA to the latest 6.0 version.