I have a react-native application, when i run locally using expo it is able to call the apis which i developed using flask and deployed on vercel. But when i build the apk of the application to run on my device it can still call the GET urls but not POST urls. I am passing all the parameters, body as required by POST method. Here is the example:

@app.route('/test_api', methods=['GET', 'POST'])
def test_api():
    print("# ---- test api ---- #")
    if request.method == 'GET':
        testData = db.child('test').get()
        to_send_list = []
        if testData:
            to_send_list.append(testData.val())
            return jsonify({'data': to_send_list, 'msg':'Got the data' ,'status_code': 200}), 200       
        else:
            return jsonify({'data': [], 'msg':'No data','status_code': 400}), 400
    elif request.method == 'POST':
        data = request.get_json()
        to_send_list = [data]
        testData = db.child('test').push(data)
        if testData:
            return jsonify({'key': testData['name'], 'msg': 'test data pushed', 'status_code': 200}), 200
        else:
            return jsonify({'key': '', 'msg': 'test data cannot be pushed', 'status_code': 417}), 417

Now when i call this api using this function:

const submitSession = async () => {
    setIsRunning(false);
    await AsyncStorage.removeItem("sessionStartTime");
    console.clear()
    const currentDate = new Date();
    console.log("Current Date: ", currentDate)
    // const formattedDate = currentDate.toISOString().split("T")[0];
    const formattedDate = currentDate.toLocaleDateString("en-CA")
    const today_new = format(new Date(), "MMM dd, yyyy");

    const sessionData = {
      date: formattedDate,
      day: id,
      name: subHead,
      exercise: workout
        ? workout.reduce((acc, item) => {
            acc[item.exercise] = checkedItems[item.id] ? "Done" : "Not Done";
            return acc;
          }, {})
        : {},
      totalTimeTaken: `${Math.floor(timer / 60)} min ${timer % 60} sec`,
      sessionTime: isAM ? "Morning" : "Evening",
    };
    
    console.log("Session Data: ")
    console.log(sessionData)
    const resp = await fetch(uploadSessionUrl, {
      method: 'POST',
      headers: {
        'Content-Type': 'application/json',
      },
      body: JSON.stringify(sessionData),
    });
    
    if (resp.ok){
      const result = await resp.json();
      setResponseModal({
        visible: true,
        message: "Data successfully added!",
        statusCode: "200"
      })
    }
    else {
      setResponseModal({
        visible: true,
        message: "Data push Failed!",
        statusCode: "404"
      })
    }
  };

I tried most of the methods i can. Like remakeing the page again, trying a test api and all but the issue still persits in POST API calls only. Any help would be appreciated.