angular material button style not working code example

Example 1: angular material button css not working

@NgModule{
  ...
  imports: [
	...
    MatButtonModule
  ],
  ...
})

Example 2: angular material toolbar with logo

<mat-sidenav-container>
  <mat-sidenav #sidenav>
    <mat-nav-list>

      <a mat-list-item [routerLink]="'/accounts'"> Accounts </a>
      <a mat-list-item [routerLink]="'/create-account'"> Create Account </a>
      <a mat-list-item [routerLink]="'/contacts'"> Contacts </a>
      <a mat-list-item [routerLink]="'/create-contact'"> Create Contact </a>
      <a mat-list-item [routerLink]="'/activities'"> Activities </a>
      <a mat-list-item [routerLink]="'/create-activity'"> Create Activity </a>
      <a mat-list-item (click)="sidenav.toggle()" href="" mat-list-item>Close</a>

    </mat-nav-list>
  </mat-sidenav>
  <mat-sidenav-content>
    <div style="height: 88vh;">

      <router-outlet></router-outlet>
    </div>
  </mat-sidenav-content>
</mat-sidenav-container>