This is an excerpt from the installation log, symptoms of a failed upgrade will look similar to this:
Action 1:20:27: MigrateFeatureStates. Migrating feature states from related applications
Action start 1:20:27: MigrateFeatureStates.
MSI (c) (28:80) [01:20:27:803]: Skipping MigrateFeatureStates action: feature settings already made
Action ended 1:20:27: MigrateFeatureStates. Return value 0.
MSI (c) (28:80) [01:20:27:803]: Skipping action: InstSuppRestoreSessionDir (condition is false)
MSI (c) (28:80) [01:20:27:803]: Doing action: InstSuppPrepareInstall
Action 1:20:27: InstSuppPrepareInstall.
Action start 1:20:27: InstSuppPrepareInstall.
Ensure your system is up to date and there are no pending Windows Updates.
In case you are experiencing upgrade issue and have already uninstalled previous version 4.x of ESET File Security, ESET Security for Microsoft SharePoint or ESET Mail Security, follow these steps to resolve it:
Install EFSW / ESHP / EMSX / EMSL 4 again
Finish all pending Windows Updates
Uninstall EFSW / ESHP / EMSX / EMSL 4
Restart operating system
Perform a fresh installation of EFSW / ESHP / EMSX / EMSL 6