Submit a form when my input is checked Angular

Hello everyone I am on rating-app component and i want to submit my form only if I have a notation checked ( 1,2,3,4,5 ) but i create all my input with an *ngFor so when i try to do it with *ngModel only an element is triggered and i don't understand why, if someone can help me it will be great !

this is my repo : https://github.com/qalimero/rating-app

My HTML :

 <main role="main">
  <div *ngIf="!display; then displayRate else displayResult"></div>
  <ng-template #displayRate>
    <div class="header-rating" role="heading">
      <fa-icon [icon]="faStar"></fa-icon>
      <h1>How did we do ?</h1>
    </div>
    <p class="text-body">
      Please let us know how we did with your support request. All feedback is 
      appreciated to help us improve our offering!
    </p>
    <form>
      <ul class="radio-wrapper">
        <li *ngFor='let radio of radios; let idx = index' [ngClass]="['radio']">
          <input [(ngModel)]="!isChecked" class="visually-hidden" id="rate_{{ idx }}" 
                 name="rate" type="radio">
          <label [ngClass]="['custom-checkbox']"
                 for="rate_{{ idx }}">{{ radio }}</label>
        </li>
      </ul>
      <button (click)="submitResult()" [disabled]="isChecked ===false" 
       type="button">SUBMIT</button>
    </form>
  </ng-template>
  <ng-template #displayResult>
    <div class="header-result">
      <img src="../../assets/images/illustration-thank-you.svg">
      <p class="resume-result">You selected 4 out of 5</p>
      <h2>Thank you!</h2>
      <p>We appreciate you taking the time to give a rating. If you ever need more 
         support, don’t hesitate to get in touch!
      </p>
    </div>
  </ng-template>
</main>

Ts :

import {Component} from '@angular/core';
import {faStar} from "@fortawesome/free-solid-svg-icons";

@Component({
  selector: 'app-rating-component',
  templateUrl: './rating.component.html',
  styleUrls: ['./rating.component.scss']
})
export class RatingComponent {
  display = false;
  faStar = faStar;
  radios = ['1', '2', '3', '4', '5'];
  isChecked = false;

  constructor() {

  }

  submitResult() {
    this.display = !this.display;
  }
}