Angular4 reactive form validation not working : <p>In pic1 I have written a input tag (line: 101) and another input tag copied from other place (line: 102)
But first input tag is working but not second one, because for second input tag there is no "ng-invalid ng-touched" class in DOM (pic2). <a href="https://i.stack.imgur.com/yM7V7.png" rel="nofollow noreferrer">pic1</a> 
<a href="https://i.stack.imgur.com/rf8mm.png" rel="nofollow noreferrer">pic2</a></p>

<pre><code>import { Component, OnInit } from "@angular/core";
import { FormGroup, FormControl, Validators } from "@angular/forms";
@Component({
 selector: "app-sign-up",
 templateUrl: "./sign-up.component.html",
 styleUrls: ["./sign-up.component.css"]
})
export class SignUpComponent implements OnInit {
ngOnInit(): void {
//this.Registration.va
}
Registration = new FormGroup({
  fullName: new FormControl("",[Validators.required])
 });
}
</code></pre>
