The specified application doesn't exist. Error (-2147220954) - Resovled!
Thank you Oracle Support!
Cause
This issue is caused by wrong HFM cluster info inherited from the environment where the HFM application was copied.
When a HFM application is copied from one environment to another, the table <ApplicationName>_USERPARAMS is also copied along. The USERPARAMS table stores user-based information such as HFM Cluster settings, Extended Analytics settings, Web Data Entry Form settings, Web Based Report Files, etc.
As a result, HFMCopyApplication will copy the HFM Cluster information settings of the environment it was copied from; when the user then opens the resulting application in the new environment, HFM will try to use those parameters, fail, and return the error.