EV agent based Backup/Restore job tries to connect to Backup Exec server if the server names have a specific pattern in the server name. The job will fail with "Unable to attach to a resource" error. If the Backup Exec server has same drive letter as the EV server, then the restore job will target restore data to Backup Exec server and fail.
0xe000848c - Unable to attach to a resource. Make sure that all selected resources exist and are online, and then try again. If the server or resource no longer exists, remove it from the selection list. Edit the selection list properties, click the View Selection Details tab, and then remove the resource.
To confirm the issue, review the beremote debug log from Backup Exec server. The following output will be visible during the resource detection:
FS_DleEV::ResolveDeviceName - DLE (EV-PTN::\\EV0101\General Mailbox Store\General Mailbox Store Ptn5@F:) Machine (BU0101)
EV0104 is the Enterprise Vault Server
BU0101 is the Backup Exec Media Server