disable FormGroup by using Validators

I had formArray checkbox on my checkboxForm, I need to disabled button submit if no checkbox are checked, I had implement custom validator on my checkboxForm, this is what I had tried;

Ts file

  get formReceivedSummons() {
    return this.checkboxForm.get('receivedSummons') as FormArray;
  }

  ngOnInit() {
    this.checkboxForm = this.formBuilder.group({
      receivedSummons: this.formBuilder.array([])
    });
    this.getReceivedSummons();
  }

  getReceivedSummons() {
    this.receivedSummonsSubscription = this.inquiryStore.summons$
      .subscribe(receivedSummons => {
        this.receivedSummons = receivedSummons;
      });
  }

  addCheckboxes() {
    this.formReceivedSummons.setValue([]);
    this.formReceivedSummons.setValidators([minSelectedCheckboxes(1)]);
    this.receivedSummons.data.items.map(x => {
      this.formReceivedSummons.push(
        this.formBuilder.group({
          itemNo: [x.itemNo],
          isChecked: false,
        }));
    });
  }


function minSelectedCheckboxes(min = 1) {
  const validator: ValidatorFn = (formArray: FormArray) => {
    const totalSelected = formArray.controls
      .map(control => control.value)
      .reduce((prev, next) => (next ? prev + next : prev), 0);

    return totalSelected >= min ? null : { required: true };
  };
  return validator;
}

I had place validators at formArray which is this.formReceivedSummons.setValidators([minSelectedCheckboxes(1)]);

this is what I had implement in html file

    <form [formGroup]="checkboxForm" (ngSubmit)="submitSelectedCheckbox()">
        <ng-container formArrayName="receivedSummons" *ngFor="let summon of formReceivedSummons.controls; let i = index">
            <ng-container [formGroupName]="i">
                <input type="checkbox" formControlName="isChecked"> 
      </ng-container>
    </ng-container>
    <button [disabled]="!checkboxForm .valid">submit</button>
</form>

my checkboxForm button have been disabled, but if I checked one checkbox it should be enabled, but it didnt. I'm not sure how to solve thw problems, could use some guide and guidance to solve this.