The cause of the “Error 1001. InstallUtilLib.dll: Unknow error.” is that the .Net framework versions to build the MSI installer and to build Custom Action dll are not the same version.
For example:
The Custom Action dll .Net framework version is 4.8.
The .NET Framework Launch Condition Property -> Version is v4.0 Client:
To resolve this problem, please change the .NET Framework Launch Condition Property -> Version to .NET Framework 4.8:
Rebuild the Printer Driver Microsoft MSI install sample.