Angular value updated in parent component, is not reflected in child component

Question

I have a custom control child component. When i try to set a value updated in parent component, the child is not getting the updated value. Please let me know what i am doing wrong here.

parent .html

<child-component
        [config]="{ getPage: getSelectInfinitePage(), multiple: true }"
        [(ngModel)]="selectedEntityItems" //in the child compoennt, this always coming as empty
        [disabled]="!hasSubjectType"
        [placeholder]="placeholderText"
        name="selectInfinite"
        (onChange)="onCustomItemChange()"
    >
    </child-component>

parent .ts

this.selectedEntityItems = ['a', 'b', 'c'];

Child component .ts (custom control using ControlValueAccessor)

writeValue(preselectedValues: ValueType): void {
    this.values = preselectedValues; //here it is always coming empty
    this.onModelChange(this.values);
}