401 unauthenticated for detect Intent dialogflow

Question

I'm getting the error of detect intent error, unauthorized 401 in the frontend, I'm using angular and chatbot framework as dialogflow Here in the code im using session as a static value, i don't have idea on the session if that is the issue, please explain to resolve it.

im following this article https://chatbotslife.com/dialogflow-v2-rest-api-communication-6cf7ab66ab36 and replicate it for my own usecase

error:

code: 401
message: "Request had invalid authentication credentials. Expected OAuth 2 access token, login 
cookie or other valid authentication credential. See https://developers.google.com/identity/sign- 
in/web/devconsole-project."
status: "UNAUTHENTICATED"
__proto__: Object

server code

// routings
const express = require("express");
const cors = require("cors");

const app = express();
app.use(cors());
// authentication
const googleAuth = require("google-oauth-jwt");
// accountinfo
const acc = require("./onlineexambot-appenginekey.json");

const getToken = async () => {
console.log("tok");
return new Promise(resolve => {
googleAuth.authenticate(
  {
    email: acc.client_email,
    key: acc.private_key,
    scopes: [
      "https://www.googleapis.com/auth/cloud-platform",
      "https://www.googleapis.com/auth/dialogflow"
    ]
  },
  (err, token) => {
    console.log(err);
    resolve(token);
  }
);
});
};

app.get("/token", async (req, res) => {
let token = await getToken();
console.log("token::", token);
res.send({ token });
});

app.listen(4000, () => {
console.log("listening on 4000");
});

FECode

    import {HttpClient } from '@angular/common/http';
    // import { } from './cookie.service'
    import {environment} from '../environments/environment'
    @Injectable({
    providedIn: 'root'
    })
    export class DfserviceService {
    accessToken:any;
    constructor(private http:HttpClient) { this.getToken()}
    public getToken(){
    this.http.get('http://localhost:4000/token').subscribe((res:any)=>{
      this.accessToken = res.token;
      console.log(res.token)
    });
    }
    public df_client_call(request){
    var config={
      headers:{
        'Authorization':"Bearer"+this.accessToken,
        'Content-Type':'applcation/json;charset=utf-8'
      }
     };
     return this.http.post ('https://dialogflow.googleapis.com/v2/projects/'+
     environment.project_id+'/agent/sessions/qwerty12345'+':detectIntent',request,config);
     }
     }

Answer 1

    'Authorization':"Bearer "+this.accessToken,

Just a minor issue is there, try adding space after Bearer as above and let me know...