I couldn't able to login since i encountered this error

Question

I am new to the firebase database, so I'm struggling right now. This is the error that I encountered:

FireSharp.Exceptions.FirebaseException: Request responded with status code=BadRequest, response={
"error" : "Invalid path: Invalid token in path"
}

at FireSharp.FirebaseClient.<>c.<.ctor>b__3_0(HttpStatusCode statusCode, String body) at FireSharp.FirebaseClient.HandleIfErrorResponse(HttpStatusCode statusCode, String content, Action`2 errorHandler) at FireSharp.FirebaseClient.Get(String path) at WRS2big_Web.LandingPage.Account.btnLogin_Click(Object sender, EventArgs e)

These are my codes:

public void btnLogin_Click(object sender, EventArgs e)
{
    try
    {
        // RETRIEVE DATA FROM ADMIN TBL
        string email = txt_email.Text;
        string pass = txt_password.Text;

        FirebaseResponse response;
        response = twoBigDB.Get("ADMIN/" + txt_email.Text);
        Session["email"] = email;
        Session["pass"] = pass;
        Response.Redirect("/Admin/AdminIndex.aspx");
        
    }
    catch (Exception ex)
    {
        Response.Write("<pre>" + ex.ToString() + "</pre>");
    }
}