ESP32 BLE Fails to Advertise or Get Detected by Mobile App in Temperature Monitoring Project

import bluetooth
from machine import Pin
import dht

sensor = dht.DHT11(Pin(4))
ble = bluetooth.BLE()
ble.active(True)

def advertise():
    adv_data = b'\x02\x01\x06' + b'\x03\x03\xaa\xfe'
    ble.gap_advertise(100, adv_data)

def send_data(temp, hum):
    data = "Temp: {}°C, Hum: {}%".format(temp, hum)
    ble.gatts_notify(0, 0, data.encode('utf-8'))

advertise()

while True:
    sensor.measure()
    temp = sensor.temperature()
    hum = sensor.humidity()
    send_data(temp, hum)