The was a subset for client apps. The Full package (which dotNetFx40_Full_x86_x64.exe includes) contains both Client Profile and Extended features (ASP.NET, advanced services). For 99% of users, the Full package is the right choice.

Ensure you have administrative rights when running the installer.

Users running legacy applications on Windows 7 that specifically require .NET 4.0 and cannot run on newer versions (4.5, 4.6, 4.8).

This error indicates that the installer is trying to pull language packs or verification files from the internet but cannot establish a connection.

Download the official Microsoft .NET Framework Repair Tool or the .NET Framework Cleanup Tool . Run the utility to wipe previous .NET states before launching the 4.0 offline installer again.