Please Verify your code is like this
Now updated the code — you can view the difference now
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Document</title>
<!--bootstrap 4.0----> <!---this is importent--->
<link rel="stylesheet" href="https://stackpath.bootstrapcdn.com/bootstrap/4.3.1/css/bootstrap.min.css" integrity="sha384-ggOyR0iXCbMQv3Xipma34MD+dH/1fQ784/j6cY/iJTQUOhcWr7x9JvoRxT2MZw1T" crossorigin="anonymous">
</head>
<style>
.border{
border: 1px solid gray;
}
</style>
<body>
<nb-card>
<nb-card-header>
<input nbInput id="search" class="search-input ml-3 mt-2 mb-2" placeholder="Search" #box (keyup)="onKey(box.value)">
</nb-card-header>
<nb-card-body>
<nb-tabset fullWidth>
<nb-tab tabTitle="TabA">
<div class="row">
<div class="col-md-2 col-sm-12 p-2 m-5 border" *ngFor="let item of list_of_detail">
<nb-card status="success" *ngIf="item.env == 'A'">
<nb-card-header> {{ item.host }}</nb-card-header>
<nb-card-body>
version: {{ item.version }}
</nb-card-body>
<nb-card-footer>{{ item.service }} | {{ item.region }}</nb-card-footer>
</nb-card>
</div>
</div>
</nb-tab>
<nb-tab tabTitle="TabB">
<div class="row">
<div class="col-md-4 col-sm-12 p-2 m-5 border" *ngFor="let item of list_of_detail">
<nb-card status="danger" *ngIf="item.env == 'B'">
<nb-card-header> {{ item.host }}</nb-card-header>
<nb-card-body>
version: {{ item.version }}
</nb-card-body>
<nb-card-footer>{{ item.service }} | {{ item.region }}</nb-card-footer>
</nb-card>
</div>
</div>
</nb-tab>
<!-----Bootstrap--> <!---this is importent--->
<script src="https://code.jquery.com/jquery-3.3.1.slim.min.js" integrity="sha384-q8i/X+965DzO0rT7abK41JStQIAqVgRVzpbzo5smXKp4YfRvH+8abtTE1Pi6jizo" crossorigin="anonymous"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/popper.js/1.14.7/umd/popper.min.js" integrity="sha384-UO2eT0CpHqdSJQ6hJty5KVphtPhzWj9WO1clHTMGa3JDZwrnQq4sF86dIHNDz0W1" crossorigin="anonymous"></script>
<script src="https://stackpath.bootstrapcdn.com/bootstrap/4.3.1/js/bootstrap.min.js" integrity="sha384-JjSmVgyd0p3pXB1rRibZUAYoIIy6OrQ6VrjIEaFf/nJGzIxFDsf4x0xIM+B07jRM" crossorigin="anonymous"></script>
<!---this is importent--->
</body>
</html>
you must add css file
<!---bootstrap 4.0----> <!---this is importent--->
<link rel="stylesheet" href="https://stackpath.bootstrapcdn.com/bootstrap/4.3.1/css/bootstrap.min.css" integrity="sha384-ggOyR0iXCbMQv3Xipma34MD+dH/1fQ784/j6cY/iJTQUOhcWr7x9JvoRxT2MZw1T" crossorigin="anonymous">
And the script is
<!-----Bootstrap--> <!---this is importent--->
<script src="https://code.jquery.com/jquery-3.3.1.slim.min.js" integrity="sha384-q8i/X+965DzO0rT7abK41JStQIAqVgRVzpbzo5smXKp4YfRvH+8abtTE1Pi6jizo" crossorigin="anonymous"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/popper.js/1.14.7/umd/popper.min.js" integrity="sha384-UO2eT0CpHqdSJQ6hJty5KVphtPhzWj9WO1clHTMGa3JDZwrnQq4sF86dIHNDz0W1" crossorigin="anonymous"></script>
<script src="https://stackpath.bootstrapcdn.com/bootstrap/4.3.1/js/bootstrap.min.js" integrity="sha384-JjSmVgyd0p3pXB1rRibZUAYoIIy6OrQ6VrjIEaFf/nJGzIxFDsf4x0xIM+B07jRM" crossorigin="anonymous"></script>
<!---this is importent--->