Why is my backend not sending the value to the frontend?

In regards to this problem: How can I pass a value from the backend to a React frontend and use that value in the CSS for the frontend?, I have another issue.

Currently, I'm working on a project where a user talks into their mic and I take the transcript and score it, and based on that score I return it to the frontend and the scale moves accordingly. For some reason the backend of my project is not passing in the value I want it to, or my frontend just isn't processing it. When my backend passes a score of like 67, the scale in my frontend doesn't move from its initial starting position. But when I manually change what the score variable is in the front end (the score is a variable in the frontend which is where I store the score passed from the backend and it can be accessed by this.state.score), it works fine and the scale moves.

Here is my python backend code:

from flask import Flask, request
from flask_cors import CORS
from flask_restful import Api, Resource

app = Flask(__name__)
api = Api(app)
cors = CORS(app, resources={r"/*": {"origins": "*"}})
app.config['CORS_HEADERS'] = 'Content-Type'


# Processes and outputs score to screen
class ProcessData(Resource):
    def processScores(self):
        transcript = request.json
        if transcript != '':
            return 78
        else:
            print("Invalid input") # debug
            return "Invalid Input"
    
    # This is the function that sends the score to the frontend
    def post(self):
        x = self.processScores()
        return x


api.add_resource(ProcessData, "/")

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

Here is my React code:

import React, { Component } from 'react';

class Product extends Component {
  constructor() {
    super();
    this.state = {
      // This is where the score is being saved
      listening: false,
      text: '',
      score: '',
    };
    this.toggleListen = this.toggleListen.bind(this);
    this.handleListen = this.handleListen.bind(this);
  }

  handleSending() {
    const options = {
      method: 'POST',
      headers: {
        'Content-Type': 'application/json',
      },
      body: JSON.stringify(this.state.text),
    };

    fetch('http://127.0.0.1:5000/', options)
      .then((response) => response.text())
      .then((json) => this.setState({ score: json }));
    this.setState({ text: '' });
  }


  render() {
    return (

        <div className="scale-container">
          <div className="bar">
            <div className="arrow-up" style={{ left: `${this.state.score}%` }}></div>
            <span></span>
          </div>
        </div>
      </div>
    );
  }
}

export default Product;

Does anyone know why this happens?