When enabling a cache or updating a cache to an image service, the following errors: "Method failed.HRESULT = 0x80004005 : Unspecified error." and "The requested capability is not supported." are returned.
This issue is longer reproducible on current versions of ArcGIS Server. If the same or similar problems are encountered on current releases (10.7.1), contact Esri Support Services to log a new bug report.