$modal is not open for the second time in Angularjs - angularjs

Question

$modal is called in the $ngonint hook. First time when controller loads, it works perfectly. But for the second time, it is not showing up when the controller loads.
Expectation:
Consider two controllers first and second.
Navigate to second controller from first controller by clicking link.
We need to show below modal when page loads whenever navigate to second controller page.
Actual Result:
For the first time, when it navigate to second controller, it showed the modal as expected. once go back to first page and come again to second controller, modal is not showed up.
Can anyone help me to solve this issue ? Thanks.
Below are the code sample:
Controller
$onInit() {this.showModal();} // Need to show modal when page loads
public showModal= function () {
var modalInstance = $modal.open({
template: ModalTemplate,
controller: [
'$scope',
'$modalInstance',
function ($scope, $modalInstance) {
$scope.answer = '';
$scope.close = function () {
$modalInstance.dismiss();
};
$scope.next = function () {
$modalInstance.close($scope.answer);
};
},
],
windowClass: 'open-account'
});
modalInstance.result.then((response) => {
console.log(response);
})
}
ModalTemplate.html
<div class="modal-header">
<button type="button" class="close" ng-click="close()" aria-hidden="true">
<fa-icon icon="times" prefix="fal" class="close-fa fa-lg"></fa-icon>
</button>
</div>
<div class="modal-body">
<div class="row">
<div class="col-sm-4">
<div class="form-group radio-group-label">
<label class="control-label">
Click
</label>
</div>
</div>
<div class="col-xs-2">
<div class="form-group">
<label class="control-label" for="answer-yes">
<input type="radio" name="answer" ng-model="answer" value="yes"
id="answer-yes" />
Yes
</label>
</div>
</div>
<div class="col-xs-2">
<div class="form-group">
<label class="control-label" for="answer-no">
<input type="radio" name="answer" ng-model="answer" value="no"
id="answer-no" />
No </label>
</div>
</div>
</div>
</div>
<div class="modal-footer">
<button class="btn btn-success" ng-disabled="!answer" ng-click="next()">Next</button>
</div>