Register a custom URL protocol in Windows doesn't open my file?

Question

I am trying to make a custom protocol to open my c# windows application through a web application following the first comment's steps here: How do I register a custom URL protocol in Windows? After setting everything up, I got to the last part where I have to type the link. Internet Explorer knows that I have to open some sort of a file but it requires a different reader.

Here is the protocol I made.

And this is the path, I have copied it, so it should be correct!

This is the folder of the program that I want to open.

Here is what happens when I go to that website. As you can see, I need to allow the browser to open the app.

And here is the problem. Any solutions to that? Of course, I can open normally the .exe file without getting any errors.