my accordion does not expand dynamically.

I think the documentation is simple, I must put a boolean in [collapsed], but in my case only the arrow changes, but the accordion is not expanded. I have a somewhat extensive code, so I preferred to create a brief example with my problem. I need open an accordion from .ts

<mdb-accordion  [multiple]="true"  *ngFor="let  item of  array"  >
   <mdb-accordion-item [collapsed]="!item.check" >
      <mdb-accordion-item-head> 
                 . 
                 .
<a (click)="fn_openAcordion(0)">1</a>
<a (click)="fn_openAcordion(1)">2</a>
<a (click)="fn_openAcordion(3)">1</a>

//this is the response of webservice that I cant modify
this.array=[
 {"name":"pedro"},
 {"name":"juan "},
 {"name":"miguel"},
]  


// I add boolean var
for(var i in this.array){
  this.array[i]["check"]=false;
}

fn_openAcordion(index){
//only changes the arrow of the accordion
 this.array[0].check=true;
}

Is strange that the accordion does not expand, I would like to know if there is a way to correct this or have a plan b. The only thing that is affected is the arrow indicating the accordion, but the accordion does not expand.