If you upgrade the Microsoft Windows operating system to a new major version, the computer on which ePO is installed can become damaged. For example, the upgrade might be from Windows Server 2008–2012.

We don't recommend that you upgrade the Windows operating system on a computer with ePO installed. Instead, use one of the following options:

• Use the ePO Disaster Recovery Snapshot function to restore an ePO server to a new computer, even if the computer is running a different operating system. For more information about the Disaster Recovery Snapshot process, see the relevant ePolicy Orchestrator 5.10 Product Guide.
   
• To transition to a new computer with the preferred operating system, follow the manual migration process described.
  For information, see KB71078 - How to migrate ePO from a 32-bit system to a 64-bit system or to a different installation path.

If you can't follow the Trellix Product recommendations, be certain that you have the backups needed to perform disaster recovery. The backups are needed if the operating system upgrade leaves ePO in an inoperable state.
 
Also, see KB66616 - ePolicy Orchestrator server backup and disaster recovery procedure.