Make sure you've installed .NET Framework Developer Pack, not a regular package.
If you're using Visual Studio, Code or other IDE, you should also install a .NET Targeting Pack.
Downloads page: https://www.microsoft.com/net/download
Related:
- The reference assemblies for framework ".NETFramework,Version=v4.6.2" were not found
- Targeting pack for .NET 4.5.2 not installed
