Using Decryption settings in MediaConvert for processing already encrypted video file with AES 256 CBC. Getting error as invalid decryption key.

I am tryin to encrypt a video file with with AES 256 CBC mode and using AWS KMS to encrypt the AES data key that was used to encrypt the video file. I have pass this encrypted file to AWS MediaConvert, it should decrypt the video on fly then transcode it. After encrypting the video using following code I am encoding encrypted data key and Initialization vector with Base64 because it is mandatory for MediaConvert. Please help in identifying the mistakes I am doing in the code or in the decryption settings or in both.

The decryption settings in MediaConvert

The error message

The code

import os
import base64
import boto3
from cryptography.hazmat.primitives import padding
from cryptography.hazmat.primitives.ciphers import Cipher, algorithms, modes
from cryptography.hazmat.backends import default_backend

# Initialize AWS KMS client
#session = boto3.Session(profile_name='your_profile_name')  # Replace with your AWS profile
#kms_client = session.client('kms')
kms_client = boto3.client('kms', region_name='us-east-1')

# Function to generate a random initialization vector (IV)
def generate_iv():
    return os.urandom(16)

# Function to pad the plaintext to a multiple of block size
def pad_data(data, block_size):
    padder = padding.PKCS7(block_size * 8).padder()
    padded_data = padder.update(data) + padder.finalize()
    return padded_data

# Function to encrypt a file using AES-CBC
def encrypt_file(filename, key):
    with open(filename, 'rb') as file:
        plaintext = file.read()

    iv = generate_iv()
    base64_iv = base64.b64encode(iv)
    print("the iv : ", iv)
    print("the iV in base 64 : ", base64_iv)
    cipher = Cipher(algorithms.AES(key), modes.CBC(iv), backend=default_backend())
    encryptor = cipher.encryptor()

    padded_plaintext = pad_data(plaintext, algorithms.AES.block_size)
    ciphertext = encryptor.update(padded_plaintext) + encryptor.finalize()
    base64_encoded_encrypted_data_key = base64.b64encode(ciphertext).decode('utf-8')
   # print("the encrypted data key ", base64_encoded_encrypted_data_key)
    with open('encrypted_'+filename, 'wb') as file:
        file.write(iv)
        file.write(ciphertext)

# Replace 'your_profile_name' with your AWS profile and 'your_key_alias' with your KMS key alias
profile_name = 'default'
#key_alias = 'your_key_alias'

# Replace 'video.mp4' with the name of your video file
filename = 'video.mp4'

# Get data key from AWS KMS
kms_response = kms_client.generate_data_key(
    KeyId= <<kms-keyid>>,
    KeySpec='AES_256'
)

data_key = kms_response['Plaintext']
base64_encoded_encrypted_data_key = base64.b64encode(data_key).decode('utf-8')
print("datakey = ", base64_encoded_encrypted_data_key)
encrypt_file(filename, data_key)
print('Encryption completed.')