I have a newly installed Exchange 2016 server on Server 2012 R2. I tried to install DUO for OWA but keep getting the error “Duo Security for OWA Integration requires ASP .NET 4.5 Enabled for IIS”. Before Exchange was installed, I had patched my servers and with that .Net 4.7.1 was installed. I went through all the prerequisites per the install documentation and all the Server options are installed for ASP 4.5. I’m not sure what else to try. Is this a compatibility issue due to having .NET 4.7.1 installed?
Do you have .NET 3.5 installed? If not, please try installing that and then retry the install.