Interceptor issue in login and logout in angular 8 - node.js

Question

In my angular application i have used login and logout concept by MEAN(mongo,Express,Angular,Node).
After login within few min if i reload the page automatically going to login page.Token is there but it is redirecting to login page.I do not know why it is happening like this.Below given my code.
auth.guard.ts:
import { Injectable } from '#angular/core';
import { CanActivate, ActivatedRouteSnapshot, RouterStateSnapshot } from
'#angular/router';
import { Observable } from 'rxjs';
import { UserService } from "../shared/user.service";
import { Router } from "#angular/router";
#Injectable({
providedIn: 'root'
})
export class AuthGuard implements CanActivate {
constructor(private userService : UserService,private router : Router){}
canActivate(
next: ActivatedRouteSnapshot,
state: RouterStateSnapshot): boolean {
if (!this.userService.isLoggedIn()) {
this.router.navigateByUrl('/login');
this.userService.deleteToken();
return false;
}
return true;
}
}
user.service.ts:
getToken() {
return localStorage.getItem('usertoken');
}
setToken(token: string) {
localStorage.setItem('token', token);
}
getToken() {
return localStorage.getItem('token');
}
deleteToken() {
localStorage.removeItem('token');
}
getUserPayload() {
var token = this.getToken();
if (token) {
var userPayload = atob(token.split('.')[1]);
return JSON.parse(userPayload);
}
else
return null;
}
isLoggedIn() {
var userPayload = this.getUserPayload();
if (userPayload)
return userPayload.exp > Date.now() / 1000;
else
return false;
}
After logged within 2 or 3 min if i refresh the page getting err.error.auth is false.Why it is happening like this?
auth.intercepter.ts:
import { HttpInterceptor, HttpRequest, HttpHandler, HttpEvent } from "#angular/common/http";
import { Injectable } from '#angular/core';
import { tap } from 'rxjs/operators';
import { Router } from "#angular/router";
import { UserService } from "../shared/user.service";
#Injectable()
export class UserAuthInterceptor implements HttpInterceptor {
constructor(private userService : UserService,private router : Router){}
intercept(req: HttpRequest<any>, next: HttpHandler) {
if (req.headers.get('noauth'))
return next.handle(req.clone());
else {
const clonedreq = req.clone({
headers: req.headers.set("Authorization", "Bearer " + this.userService.getToken())
});
return next.handle(clonedreq).pipe(
tap(
event => { },
err => {
if (err.error.auth == false) {
this.router.navigateByUrl('/login'); //After login within 2 or 3 min if i refresh or reload the page this is working.I do not know why this is calling on reload the page
}
})
);
}
}
}