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I'm using ngx-chips with autocompleteItems for tags input, but after adding the first tag, the dropdown is not appearing anymore and also there is no error in the console.

HTML

<tag-input
 [ngModel]="columnsToIgnore"
 [ngModelOptions]="standalone: true"
 [placeholder]="'Enter variables to ignore'"
 [secondaryPlaceholder]="'Enter variables to ignore'"
 [onlyFromAutocomplete]="true"
 (onAdd)="addIgnoreColumn($event)"
 (onRemove)="removeIgnoreColumn($event)"
 theme='bootstrap'>
 <tag-input-dropdown
 [autocompleteItems]="selectedDataset.schema.columns"
 [displayBy]="'name'"
 [focusFirstElement]="true">
 <ng-template let-item="item" let-index="index">
 item.name : item.type 
 </ng-template>
 </tag-input-dropdown>
</tag-input>

when adding the first tag, the dropdown appears

but when trying to add a second one, the dropdown does not appear

Stackblitz

Since you are using the complex object as options you should use identifyBy through which ngx-chips will compare the selected items with provided options.

 <tag-input
 [ngModel]="columnsToIgnore"
 [ngModelOptions]="standalone: true"
 [placeholder]="'Enter variables to ignore'"
 [secondaryPlaceholder]="'Enter variables to ignore'"
 [onlyFromAutocomplete]="true"
 (onAdd)="addIgnoreColumn($event)"
 (onRemove)="removeIgnoreColumn($event)"
 theme='bootstrap'>
 <tag-input-dropdown
 [autocompleteItems]="selectedDataset.schema.columns"
 [displayBy]="'name'"
 [identifyBy]="'name'" <!-- use any property of object -->
 [focusFirstElement]="true">
 <ng-template let-item="item" let-index="index">
 item.name : item.type 
 </ng-template>
 </tag-input-dropdown>
</tag-input>

Working copy is here - https://stackblitz.com/edit/angular-icraz4