Erro no validador assíncrono

Boa tarde galera,

estou seguindo o curso, de Angular parte 2: Autenticação, Forms e lazy loading,

na parte de criar validador assíncrono tive um problema,

segue o erro do console:

Failed to load resource: the server responded with a status of 404 (Not Found)

ERROR HttpErrorResponseerror: {message: "route /user/existis/sds does not exists!"}
message: "route /user/existis/sds does not exists!"
__proto__: Objectheaders: 
HttpHeaders {normalizedNames: Map(0), lazyUpdate: null, lazyInit: ƒ}
message: "Http failure response for http://localhost:3000/user/existis/sds: 404 Not Found"
name: "HttpErrorResponse"ok: falsestatus: 404statusText: "
Not Found"url: "http://localhost:3000/user/existis/sds"__proto__: HttpResponseBase
defaultErrorLogger @ core.js:1598

A minha API esta sendo executada, e retorna o seguinte json no caminho

{
message: "route /user/existis/sds does not exists!"
}

Segue meu singup.component.ts :

@Component({
    selector: 'ap-singup',
    templateUrl: 'signup.component.html',
    styleUrls: ['singup.component.css']
})

export class SingUpComponet implements OnInit {

    singupForm: FormGroup;

    constructor(
        private userNotTakenValidatorService: UserNotTakenValidatorService,
        private formBuilder: FormBuilder) { }


    ngOnInit(): void {
        this.singupForm = this.formBuilder.group({

            email: ['',
                [
                    Validators.required,
                    Validators.email
                ]
            ],
            fullName: ['',
                [
                    Validators.required,
                    Validators.minLength(2),
                    Validators.maxLength(50)
                ]
            ],
            userName: ['',
                [
                    Validators.required,
                    Validators.minLength(2),
                    Validators.maxLength(30),
                    lowerCaseValidator,
                    Validators.pattern(/[a-z0-9_\-]+$/)
                ],                
                this.userNotTakenValidatorService.checkUserNameTaken()

            ],
            password: ['',
                [
                    Validators.required,
                    Validators.minLength(8),
                    Validators.maxLength(14)
                ]
            ]
        });
    }
}

segue o meu template:

...
    <div class="form-group">
        <input formControlName="userName" placeholder="user name" class="form-control">
        <ap-vmessage *ngIf="singupForm.get('userName').errors?.required" text="userName is required">
        </ap-vmessage>
        <ap-vmessage *ngIf="singupForm.get('userName').errors?.minlength" text="Minimun length is 2">
        </ap-vmessage>
        <ap-vmessage *ngIf="singupForm.get('userName').errors?.maxlength" text="Max length is 30">
        </ap-vmessage>
        <ap-vmessage *ngIf="singupForm.get('userName').errors?.lowerCase" text="must be lower case">
        </ap-vmessage>
        <ap-vmessage 
            *ngIf="singupForm.get('userName').errors?.userNameTaken" 
            text="UserName already taken">
        </ap-vmessage>
        <small *ngIf="singupForm.get('userName').valid" class="text-success" >User avaliable</small>

    </div>
...

Quando uso o input userName no template aparece erro 404 no console, com o json acima, acredito que o erro seja na API.