Fetch API not working on React (localhost)

I'm facing a problem, for some reason my API failed to fetch. The server side is on C# and SQL, everything works fine there, but when I am trying to connect between them on React, it fails. my local host url is : http://localhost:50434/api/users

My code is:

var url = "http://localhost:50434/api/users";

   btnLogin = async () => {
    console.log(1);

    console.log(this.state.EmailValue + "," + this.state.PasswordValue);

    let s = await this.checkUserDetails(
      this.state.EmailValue,
      this.state.PasswordValue
    );
    console.log("returned value=" + s);

    if (s != null) {
      this.setState({ user_id: s.user_id });
      console.log("user_id is =" + this.state.user_id);
      this.setState({ showErrLbl: false }, () => {
        this.props.history.push({
          pathname: "/DrawPage/",
          state: { UserObj: s }
        });
      });
      
      console.log("h1");
    } else {
      console.log("err login!");
      this.setState({ showErrLbl: true });
    
    } };
  
  checkUserDetails = async (Email, Password) => {
    let returnedObj = null;
    console.log("we are in func checkUserDetails, email = " + Email);

    await fetch(url + `?email=${Email}&pass=${Password}`, {
      method: "GET", // 'GET', 'POST', 'PUT', 'DELETE', etc.
      headers: new Headers({
        "Content-Type": "application/json",
        Accept: "application/json",
      }),
    }) // Call the fetch function passing the url of the API as a parameter
      .then((resp) => resp.json()) // Transform the data into json
      .then(function (data) {
        console.log("meow");
        console.log(data);
        if (data != null) {
          console.log(data.Email);
          console.log(data.Password);
          returnedObj = data;
        } else {
          console.log("wrong email or password!");
          returnedObj = null;
        }
      })
      .catch(function (err) {
        alert(err);
      });

    return returnedObj;
  };

Thanks for all the helpers