When running demo application I am getting: This localhost page can’t be found

I cloned the sample application from GitHub - radzenhq/radzen-blazor: Radzen Blazor is the most sophisticated free UI component library for Blazor, featuring 100+ native components including DataGrid, Scheduler, Charts, and advanced theming with full support for Material Design and Fluent UI.

and opened the radzen.sl and ran it using radzenBlazorDemos as the starting project. But I am getting this error:

This localhost page can’t be found

No web page was found for the web address: https://localhost:7227/

HTTP ERROR 404

what am I doing wrong here?

That's the problem. You shouldn't use that project as a starting point. Check here

Thanks. I used the suggested solution and now, I can run and see the output, but when I click on a component, I get this error:

Do you have any idea why I am getting this error?

Actually this is an error which we are trying hard to reproduce at our side (reported by other users: RadzenLayout Calling NavigateTo Throws Error - #13 by korchev)

Which solution did you open? Radzen.Server.sln?

Yes, I am using Radzen.server.

Thanks. We have managed to fix that (mentioned in the other thread).