not able to mount database

Couldn't mount the database that you specified. Specified database: EPCC-Standard-DB04; Error code: An Active Manager o peration failed. Error The database action failed. Error: Operation failed with message: MapiExceptionCallFailed: Unabl e to mount database. (hr=0x80004005, ec=-550) . [Database: EPCC-Standard-DB04, Server: EPC-PL1-MBX035V.epcco.com.sa]. + CategoryInfo : InvalidOperation: (EPCC-Standard-DB04:ADObjectId) [Mount-Database], InvalidOperationExce ption + FullyQualifiedErrorId : 8C91930,Microsoft.Exchange.Management.SystemConfigurationTasks.MountDatabase