error in angular Material and app-root is empty

Question

hello everyone I'm a beginner in Angular and I used angular material component but nothing appear in browser and when I inspect I found app-root empty any solutions?

this is app.module.ts

import { BrowserModule } from '@angular/platform-browser';
import { NgModule } from '@angular/core';
import {BrowserAnimationsModule} from '@angular/platform-browser/animations';

import {FlexLayoutModule} from '@angular/flex-layout';
import {MatToolbarModule} from '@angular/material/toolbar'; 
import { AppComponent } from './app.component';
import { MenuComponent } from './menu/menu.component';
import { MatListModule } from '@angular/material/list';
//import 'hammerjs';

@NgModule({
  declarations: [
    AppComponent,
    MenuComponent
  ],
  imports: [
    BrowserModule,
    BrowserAnimationsModule,
    FlexLayoutModule,
    MatToolbarModule,
    MatListModule
  ],
  providers: [],
  bootstrap: [AppComponent]
})
export class AppModule { }

this is app.component.html:

<h1>Title 1</h1>
<app-menu></app-menu>