After some recent Windows Updates, the K2 Server service is not starting up successfully and the following error appears:
Existence of .NET Framework 4.7.1 was confirmed via registry key as per:
K2 blackpearl version 4.6.11 is not compatible/supported with .NET Framework 4.7/4.7.1 as per:
The following Windows KBs were recently installed on this Windows 2012 R2 server:
As K2 Blackpearl version 4.6.11 is only compatible/supported with .NET Framework 4.6 and earlier, the recent Windows updates were uninstalled and the server restarted to resolve the issue.
K2 Blackpearl version 4.7 and K2 Five is compatible with .NET Framework 4.7; however if on .NET Framework 4.7.1, then the applicable Fix Packs or later Fix Packs can be applied to resolve the issue:
K2 Blackpearl 4.7 - https://help.k2.com/kb002132
K2 Five - http://help.k2.com/kb002137