Angular2 Router error: cannot find primary outlet to load 'HomePage'

You have an error in your app.component.ts Looks like you declared a directive in the providers array.

import { Component } from '@angular/core';
import { ROUTER_DIRECTIVES } from '@angular/router';

@Component({
    selector: 'app',
    template: `
        <p>Angular 2 is running...</p>
        <!-- Routed views go here -->
        <router-outlet></router-outlet>
        `,
     directives: [ROUTER_DIRECTIVES] //here
})
export class AppComponent {
}

It should be directives metadata instead of providers,

directives: [ROUTER_DIRECTIVES]

Although @JS_astronauts already provided a solution, I think it would be instructive to explain the error...

The primary outlet is set when Angular parses an HTML template and finds directive RouterOutlet, i.e., when it finds RouterOutlet's selector: <router-outlet></router-outlet>.

Although your template does contain <router-outlet></router-outlet>, your component does not contain directives: [ROUTER_DIRECTIVES], so Angular won't look for any of the directives defined by that constant:

export const ROUTER_DIRECTIVES = [RouterOutlet, RouterLink, RouterLinkWithHref, 
 RouterLinkActive];

So when Angular parses AppComponent's HTML templates, if it doesn't recognize <router-outlet></router-outlet> so it just ignores it. Later, when Angular tries to render the default route component (HomePage), it complains because doesn't know where to put it.

---

This error can also happen if you have a typo in your element selector, e.g.:

<roter-outlet></roter-outlet>

In this case, even if your directives array is set correctly, Angular will never find the required <router-outlet> element.