Sending Data from JQuery in Javascript to a python Script using Flask

I got the following problem. I created a python script a while ago that allowed me to download a youtube video. Then i thought it would be cool if I created my own firefox addon working with the script to download the videos directry from the browser. So I started out and watched some tutorials and realized i could only work with js to create an addon. The I looked for a solution to send the data from my Javascript to my python script and then download the video. I then started with an AJAX Post method which I found out would be the best for my case but it just doesnt do anything. I tried multiple things to get it to work but I dont get anything returned. Here is my code(JavaScript):

console.log("Loaded Successfully!");
function postData(jsdata) {
    $.ajax({
        type: "POST",
        url: "/receivedata",
        data: { "myData": jsdata },
        success: callbackFunc
    });
}
function callbackFunc(response) {
    console.log(response);
}
postData('Hello')
console.log("Sent data successfully");

Here is the python script:

import flask
import json
from flask import request

app = flask.Flask(__name__)

@app.route('/receivedata/', methods=["GET", "POST"])
def receivedata_():
    if request.method == "POST":
        print(request.form["myData"])
        Message = {"Message":"Hello World"}
        return Message

if __name__ == "__test__":
    app.run(debug=True)

And if you need it heres my manifest.json:

{
  "manifest_version": 2,
  "name": "Test",
  "version": "1.0",
  "description": "Test Addon!",
  "content_scripts": [
    {
      "matches": ["*://*.youtube.com/watch?*"],
      "js": ["test.js"]
    }
  ],

  "permissions": [
    "*://youtube.com/*"
  ]

}