When I was trying to install SharePoint Server 2016 (this also applies to SharePoint 2013) on a Windows Server 2012 R2 machine I got this error message:

Setup is unable to proceed due to the following error(s):
This product requires Microsoft .Net Framework 4.5.


But the .Net Framework was already installed. So why I’m seeing this error? Because my version of the .Net Framework was above 4.6 which isn’t recognized by the SharePoint setup.

The solution is to uninstall the Microsoft .NET Framework 4.6 or higher through Programs and Features > Installed updates. Depending on the installed .Net version you need to uninstall the corresponding KB:
.NET Framework 4.6: KB3045563
.NET Framework 4.6.1: KB3102467
.NET Framework 4.6.2: KB3151864

Make sure automatic update on Windows is disabled – you shouldn’t use this function on servers anyway. Restart the server(s). Then use the web installer for the .NET Framework 4.5.2 to install the lower .Net version. Everything should be working fine now.