Fix

src/app/participant-room/participant-room.component.html

 <div fxLayout="column" fxLayoutAlign="start" fxLayoutGap="20px" fxFill>
   <div fxLayout="row" fxLayoutAlign="center">
     <mat-progress-spinner *ngIf="isLoading" mode="indeterminate"></mat-progress-spinner>
+    
     <mat-card *ngIf="room">
       <mat-card-header fxLayoutAlign="center">
         <mat-card-title><h3 class="subheading-2">{{ room.name }}</h3></mat-card-title>