Starting a radius validation server from the gateway user interface (UI) results in 'failed to start' or '<validation server> was not started'. 

The vipegconsole.log shows the error:  

ERROR "2019-02-18 01:15:01.674 GMT+0800" 172.21.2.204 vipegconsole 1965994315 2541f76cd7759030 18784  "actor="loggedinusername",text=Could not start server: "validationservername""

As a result of the service not starting, no logs are written to the validation server logs

To test, open a command prompt and navigate to \Program Files (x86)\Symantec\VIP_Enterprise_Gateway\Validation\bin\, then run the command:

vsauthstartserver.exe -ValidationServerName "NameofValidationServer"

This will result in the System Error:  The program can't start because MSVCR100.dll is missing from your computer.  Try reinstalling the program to fix this problem. Or, The code execution cannot proceed because MSVCR100.dll was not found.

A prerequisite of VIP EGW is Microsoft Visual C++ 2010 x86. If this becomes corrupt or is uninstalled by another application using the same components, VIP EG validation services, IdP services, and other VIP EG components will not function properly. 

• Stop all VIP EG services.  
• Download and install Microsoft Visual C++ 2010 Redistributable Package (x86) from Microsoft at the Microsoft Download Center (note: this is an external link).
• Start the VIP Services.