https://stackblitz.com/edit/primeng-dropdown-demo?file=src%2Fapp%2Fapp.component.html
When i wrap the following code in </form element, the drop collapses.
<h5>Advanced with Templating, Filtering and Clear Icon</h5>
<p-dropdown [options]="countries" [(ngModel)]="selectedCountry" optionLabel="name" [filter]="true" filterBy="name"
[showClear]="true" placeholder="Select a Country">
<ng-template pTemplate="selectedItem">
<div class="country-item country-item-value" *ngIf="selectedCountry">
<div>{{selectedCountry.name}}</div>
</div>
</ng-template>
<ng-template let-country pTemplate="item">
<div class="country-item">
<div>{{country.name}}</div>
</div>
</ng-template>
</p-dropdown>