NI software is signed with a SHA-256 certificate. Windows 7 SP1, Windows Embedded Standard 7 SP1, and Windows Server 2008 R2 SP1 require Microsoft updates to support SHA-256.
To prevent this issue happen, please refer Microsoft KB3033929
for more information to install these updates. Kindly make sure had installed these updates before you start NI-FGEN 20.0 installation.