ValueError: MAC check failed pycryptodom

Question

Can anyone help me correct this error.I am using python 3.9 and pycryptodome to make a pyqt5 gui project. Here is the code:

from Crypto.Cipher import AES
import scrypt
import os


class AESCipher:
    def __init__(self, password):
        self.password = str.encode(password)

    def encrypt_AES_GCM(self, msg):
        kdfSalt = os.urandom(16)
        secretKey = scrypt.hash(self.password, kdfSalt, N=16384, r=8, p=1, buflen=32)
        aesCipher = AES.new(secretKey, AES.MODE_GCM)
        ciphertext, authTag = aesCipher.encrypt_and_digest(msg)
        # return kdfSalt, ciphertext, aesCipher.nonce, authTag
        return ciphertext

    def decrypt_AES_GCM(self, cipherText):
        kdfSalt, ciphertext, nonce, authTag = cipherText, cipherText, cipherText, cipherText
        secretKey = scrypt.hash(self.password, kdfSalt, N=16384, r=8, p=1, buflen=32)
        aesCipher = AES.new(secretKey, AES.MODE_GCM, nonce)
        plaintext = aesCipher.decrypt_and_verify(ciphertext, authTag, output=None)
        return plaintext

i am calling functions from this class as follows:

 def decodeImage(self):
        cipher = self.cipher()
        if cipher == None:
            return
         
        obj = LSB(self.image)

        c = obj.extract()
        cipherText = base64.decodebytes(c.encode("utf-8"))
        print('Cipher text: ', cipherText)
        msg = cipher.decrypt_AES_GCM(cipherText)

        # show decoded secret message to message input box
        self.ui.messageOutput.clear()
        self.ui.messageOutput.insertPlainText(msg.decode('utf8'))
 def encodeImage(self):
        message = self.ui.messageInput.toPlainText()
        # Make msg length a multiple of 16 by adding white space at the end
        if len(message) % 16 != 0:
            message += (" " * (16 - len(message) % 16))


        cipher = self.encode_Cipher()
        if cipher is None:
            return

        cipherText = cipher.encrypt_AES_GCM(message.encode("utf-8"))
        print('Cipher text: ', cipherText)
        print('Message: ', message)
        self.ui.messageInput.insertPlainText(cipherText.hex())

        obj = LSB(self.eimage)
        obj.embed(base64.encodebytes(cipherText).decode("utf-8"))
        self.ui.messageInput.clear()
        self.eimage = obj.image

        # preview image after cipher text is embedded
        self.encode_updateImage()
        QMessageBox.about(self, "Info", "Encoded")

I am getting the error when i try to decode which in this case involves decryption. Error is as follows:

Traceback (most recent call last):
  File "C:\Users\ntc\Desktop\HIT 400\Capstone Desing\Capstone Design HIT 400\FinalApp.py", line 455, in decodeImage
    msg = cipher.decrypt_AES_GCM(cipherText)
  File "C:\Users\ntc\Desktop\HIT 400\Capstone Desing\Capstone Design HIT 400\aesSteg.py", line 22, in decrypt_AES_GCM
    plaintext = aesCipher.decrypt_and_verify(ciphertext, authTag, output=None)
  File "C:\Users\ntc\AppData\Roaming\Python\Python39\site-packages\Crypto\Cipher\_mode_gcm.py", line 567, in decrypt_and_verify
    self.verify(received_mac_tag)
  File "C:\Users\ntc\AppData\Roaming\Python\Python39\site-packages\Crypto\Cipher\_mode_gcm.py", line 508, in verify
    raise ValueError("MAC check failed")
ValueError: MAC check failed