Steps to Upgrade the .net Framework to 4.7.2 OR 4.8
1. First Download the .NET Framework from https://dotnet.microsoft.com/download/dotnet-framework
2. Install on the Server.
3. Login to the Plesk and go to "Tools & Settings" > "Server Components" and refresh the components using the refresh button
4. After update, it will reflect in "Web Script" section at the server component page.
All done!!!