Having trouble with jsonify in Flask

Question

I am fairly new to Flask and am currently working on a project whose goal is to transcribe mp3 files into JSON. I decided to attempt to use Flask, but it's been more challenging than I thought.

As of right now, I am able to display a example JSON file in one of my html pages, but I have not been able to format it. I looked at some previous answers that told me to use jsonify, but it hasn't worked apparently. If you guys could give me a hand, any kind of comment would be really apreciated. Here is my code:

from flask import Flask, render_template, url_for, request, redirect, json, jsonify
import json
import os
from pathlib import Path

app = Flask(__name__)

@app.route('/')
def index():
    return render_template('index.html')

@app.route('/upload', methods=['POST'])
def upload():
    file = request.files['inputFile']
    if Path(file.filename).suffix == '.mp3':
        filename = os.path.join(app.static_folder, 'data', 'json_test.json')
        with open(filename) as json_test:
            data = json.load(json_test)
        return render_template('index2.html', data=data)
    else:
        return render_template('erro.html')

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