For enabling .Net Core on a website, you only need to do one thing.
Disable Classic ASP via the Hosting settings in the Plesk control panel. The steps are provided below:
1- Login to Plesk Control Panel.
2- Click Websites & Domains on the left panel.
3- For the website that needs .net core enabled, select Hosting Settings.
4- Under Web Scripting and Statistics, un-check both Microsoft ASP support and Microsoft ASP.NET support (Version) checkboxes.
5- Click OK.
