How to solve the Let’s Encrypt SSL on ASP.NET Core

Article Number: 314 | Rating: 4/5 from 1 votes | Last Updated: Tue, Sep 23, 2025 at 10:57 PM

Problem: Let's Encrypt SSL fails to work even it has been activated on the Control Panel

Solution:
This solution applies to ASP.NET Core application with MVC
The problem is that Let's Encrypt SSL targets a folder .well-know inside the application. As it does not exist on the httpdocs, and that no route is targeting it, MVC will return a 404 error message and then SSL Certificate will not work.

So the trick is to add the following code on the configure method from startup.cs

app.UseStaticFiles(new StaticFileOptions

{

FileProvider = new PhysicalFileProvider(Path.Combine(Directory.GetCurrentDirectory(), @".well-known")),

RequestPath = new PathString("/.well-known"),

ServeUnknownFileTypes = true // serve extensionless file

});

And you also need to add the folder to the root of the website

As Let's Encrypt SSL is a new feature to the Plesk Control Panel, occasionally, it will not work fine. We still highly recommend our customer to use a paid SSL for higher reliability and security reason

If there is any further issue, please open a support ticket via our Help Desk System