Veeam Agent for Windows Installation fails with "Error 1920.Service Veeam Agent for Microsoft Windows (VeeamEndpointBackupSvc) failed to start" on Windows Server 2012 R2/8.1

Veeam Agent for Windows 5.0.0.4301 installation and update fails.

• An installation managed from the Veeam backup server fails with the following error:
  Installing package Veeam Agent for Windows Error: Error 1920.Service Veeam Agent for Microsoft Windows (VeeamEndpointBackupSvc) failed to start.  Verify that you have sufficient privileges to start system services.
• A standalone manual installation fails with:
  Installation failed. Installation was interrupted, or something did not work as expected.

There is a certain Windows update which must be installed on the Microsoft Windows 2012 R2 operating system that is required for Veeam Agent for Windows functionality - KB2919355.

The update contains necessary Universal C Runtime components that are required for Veeam Agent for Windows 5.0.0.4301.

If the update is not installed, software components will not function properly:

Service cannot be started. System.IO.FileNotFoundException: Could not load file or assembly 'CInterop.VeeamLicense.dll' or one of its dependencies. The specified module could not be found.
File name: 'CInterop.VeeamLicense.dll'

Install the following missing Windows update KB2919355 for Microsoft Windows Server 2012 R2.

If the issue persists or you work with another OS build, please, make sure the OS is up to date, install all other missing Windows updates and report the issue to Veeam Technical Support.