Im using python script in my ubuntu system, to connect to BLE device and get notification from device. The problem now I'm facing is I enabled the notification but still I don't get any notification. and I'm sure that I enabled notification for required UUID This is the code:

import struct
import time
import sys
import argparse
from Crypto.Cipher import AES
from bluepy.btle import Peripheral, DefaultDelegate, ADDR_TYPE_RANDOM
from pprint import pprint
from binascii import hexlify


import binascii

import os

import time

def encrypt(key, data):
    key = bytes.fromhex(key)
    msg = bytes.fromhex(data)
    cipher = AES.new(key, AES.MODE_ECB)
    msg_en = cipher.encrypt(msg)
    return msg_en.hex()


def decrypt(key, data):
    key = bytes.fromhex(key)
    decipher = AES.new(key, AES.MODE_ECB)
    # byte_data=bytes.fromhex("6f552132e2af0042ab6098c2f4e738e0")
    # Decipher akzeptiert und Binary kein Hex
    msg_dec = decipher.decrypt(binascii.unhexlify(data))
    return msg_dec.hex()

def crc16(data: bytes):
    '''
    CRC-16 (CCITT) implemented with a precomputed lookup table
    '''
    table = [
        0x0000, 0x1021, 0x2042, 0x3063, 0x4084, 0x50A5, 0x60C6, 0x70E7, 0x8108, 0x9129, 0xA14A, 0xB16B, 0xC18C, 0xD1AD, 0xE1CE, 0xF1EF,
        0x1231, 0x0210, 0x3273, 0x2252, 0x52B5, 0x4294, 0x72F7, 0x62D6, 0x9339, 0x8318, 0xB37B, 0xA35A, 0xD3BD, 0xC39C, 0xF3FF, 0xE3DE,
        0x2462, 0x3443, 0x0420, 0x1401, 0x64E6, 0x74C7, 0x44A4, 0x5485, 0xA56A, 0xB54B, 0x8528, 0x9509, 0xE5EE, 0xF5CF, 0xC5AC, 0xD58D,
        0x3653, 0x2672, 0x1611, 0x0630, 0x76D7, 0x66F6, 0x5695, 0x46B4, 0xB75B, 0xA77A, 0x9719, 0x8738, 0xF7DF, 0xE7FE, 0xD79D, 0xC7BC,
        0x48C4, 0x58E5, 0x6886, 0x78A7, 0x0840, 0x1861, 0x2802, 0x3823, 0xC9CC, 0xD9ED, 0xE98E, 0xF9AF, 0x8948, 0x9969, 0xA90A, 0xB92B,
        0x5AF5, 0x4AD4, 0x7AB7, 0x6A96, 0x1A71, 0x0A50, 0x3A33, 0x2A12, 0xDBFD, 0xCBDC, 0xFBBF, 0xEB9E, 0x9B79, 0x8B58, 0xBB3B, 0xAB1A,
        0x6CA6, 0x7C87, 0x4CE4, 0x5CC5, 0x2C22, 0x3C03, 0x0C60, 0x1C41, 0xEDAE, 0xFD8F, 0xCDEC, 0xDDCD, 0xAD2A, 0xBD0B, 0x8D68, 0x9D49,
        0x7E97, 0x6EB6, 0x5ED5, 0x4EF4, 0x3E13, 0x2E32, 0x1E51, 0x0E70, 0xFF9F, 0xEFBE, 0xDFDD, 0xCFFC, 0xBF1B, 0xAF3A, 0x9F59, 0x8F78,
        0x9188, 0x81A9, 0xB1CA, 0xA1EB, 0xD10C, 0xC12D, 0xF14E, 0xE16F, 0x1080, 0x00A1, 0x30C2, 0x20E3, 0x5004, 0x4025, 0x7046, 0x6067,
        0x83B9, 0x9398, 0xA3FB, 0xB3DA, 0xC33D, 0xD31C, 0xE37F, 0xF35E, 0x02B1, 0x1290, 0x22F3, 0x32D2, 0x4235, 0x5214, 0x6277, 0x7256,
        0xB5EA, 0xA5CB, 0x95A8, 0x8589, 0xF56E, 0xE54F, 0xD52C, 0xC50D, 0x34E2, 0x24C3, 0x14A0, 0x0481, 0x7466, 0x6447, 0x5424, 0x4405,
        0xA7DB, 0xB7FA, 0x8799, 0x97B8, 0xE75F, 0xF77E, 0xC71D, 0xD73C, 0x26D3, 0x36F2, 0x0691, 0x16B0, 0x6657, 0x7676, 0x4615, 0x5634,
        0xD94C, 0xC96D, 0xF90E, 0xE92F, 0x99C8, 0x89E9, 0xB98A, 0xA9AB, 0x5844, 0x4865, 0x7806, 0x6827, 0x18C0, 0x08E1, 0x3882, 0x28A3,
        0xCB7D, 0xDB5C, 0xEB3F, 0xFB1E, 0x8BF9, 0x9BD8, 0xABBB, 0xBB9A, 0x4A75, 0x5A54, 0x6A37, 0x7A16, 0x0AF1, 0x1AD0, 0x2AB3, 0x3A92,
        0xFD2E, 0xED0F, 0xDD6C, 0xCD4D, 0xBDAA, 0xAD8B, 0x9DE8, 0x8DC9, 0x7C26, 0x6C07, 0x5C64, 0x4C45, 0x3CA2, 0x2C83, 0x1CE0, 0x0CC1,
        0xEF1F, 0xFF3E, 0xCF5D, 0xDF7C, 0xAF9B, 0xBFBA, 0x8FD9, 0x9FF8, 0x6E17, 0x7E36, 0x4E55, 0x5E74, 0x2E93, 0x3EB2, 0x0ED1, 0x1EF0
    ]

    crc = 0xFFFF
    for byte in data:
        crc = (crc << 8) ^ table[(crc >> 8) ^ byte]
        # important, crc must stay 16bits all the way through
        crc &= 0xFFFF
    return hex(crc)

class MyDelegate(DefaultDelegate):
    def __init__(self):
        DefaultDelegate.__init__(self)
        # ... initialise here

    def handleNotification(self, cHandle, data):
        # ... perhaps check cHandle
        # ... process 'data'
        print("hello 123")
        return


key1 = '535a594c574c2d4d696e657754656368'
CCCD_UUID=0x2902
mac_addr="AC:23:3F:AA:3C:C7"
service_UUID="7f280001-8204-f393-e0a9-e50e24dcca9e"
handle_1d = "7f280002-8204-f393-e0a9-e50e24dcca9e"
device =Peripheral(mac_addr,addrType="public")
device.setDelegate(MyDelegate())


svc=device.getServiceByUUID(service_UUID)
print(svc)
define_char = svc.getCharacteristics(handle_1d)[0]
print(define_char)
# desc_notification = define_char.getDescriptors(forUUID=CCCD_UUID)[0]
desc_notification = define_char.getDescriptors()[0]
pprint(desc_notification)

                            #1. enable notification
desc_notification.write(b"\x01\x00", True)

                            #2.read encrypted data
enc_data=define_char.read().hex()
print("encrypted data read", enc_data)
dec_data=decrypt(key1,enc_data)
print("decrypted data read",dec_data)
                            #3. write encrypted data
mac_rcv=dec_data[:12]
temp=str(mac_rcv)+str(os.urandom(8).hex())
crc=str(crc16(bytes.fromhex(temp)))
print("crc for ",temp,"is",crc)
if(len(crc[2:])==3):
    temp=temp+"0"+crc[2:]
else:
    temp=temp+crc[2:]
enc_data=encrypt(key1,temp)
# data_to_send=struct.pack('<18s', b'\x01\x08' + _KEY)
define_char.write(bytes.fromhex(enc_data))
print("encrypted data sent",enc_data)
print("Data sent")


                            #4. write random number with encrypted
random_data=os.urandom(16).hex()
define_char.write(bytes.fromhex(random_data))
print("random data sent",random_data)
print("Data sent")

                            #5. enable notification to receive data
while True:
    if device.waitForNotifications(5.0):
        continue
    
        
device.disconnect()
print('Done')

as one can see I enabled notification. So what to do now? any information is needed please let me know this is the output:

Service <uuid=7f280001-8204-f393-e0a9-e50e24dcca9e handleStart=27 handleEnd=30>
Characteristic <7f280002-8204-f393-e0a9-e50e24dcca9e>
<bluepy.btle.Descriptor object at 0x7f26ace17730>
encrypted data read 1bd8f17131eb740cb25dbdcd1ea71f7f
decrypted data read ac233faa3cc77a16b0befebd2e1c0410
crc for  ac233faa3cc783f5b6718e43515d is 0xc81b
encrypted data sent b6715a3b6c4ad4bfdedf4518de0847be
Data sent
random data sent 008b9adfb7d66b470d85c4451d46e6ee
Data sent
Traceback (most recent call last):
  File "/home/subhash/Downloads/Visual_studio/Hack_Minew.py", line 124, in <module>
    if device.waitForNotifications(5.0):
  File "/usr/local/lib/python3.8/dist-packages/bluepy/btle.py", line 560, in waitForNotifications
    resp = self._getResp(['ntfy','ind'], timeout)
  File "/usr/local/lib/python3.8/dist-packages/bluepy/btle.py", line 407, in _getResp
    resp = self._waitResp(wantType + ['ntfy', 'ind'], timeout)
  File "/usr/local/lib/python3.8/dist-packages/bluepy/btle.py", line 362, in _waitResp
    raise BTLEDisconnectError("Device disconnected", resp)
bluepy.btle.BTLEDisconnectError: Device disconnected

and one more thing is if my BLE device is not engaged in communication while in connection, it will terminate the connection after a few seconds.