May have FINALLY gotten the silent install working, though I'm not sure if it has to do with pushing it to our lab computers in the same OU or enabling the ANSYS 19.1 integration step.  Those are the only things that are different between this .iss file and the old one.  I created the .iss file on a lab machine that had ANSYS 19.1 installed, so that allowed me to enable the integration.  I have pushed it to multiple lab computers, without any issues as of yet.  Thank you for all of your suggestions.