How would I fix my Vigenere Cipher Decryption

Question

I'm having an issue with Vigenere Cipher Decryption, When an encrypted message is decrypted, the decrypted message is not printed, but the encrypted is?

I cant seem to see why this dose not work. But its probably a simple issue. I think the issue is in the main decrypt function. Help would be much appreciated

Encryption works fine

def encrypt_key(message, key):    
    i = 0
    empty_key = '' # empty key to append to 

    # turn characters into index
    for characters in message:
        if characters.isalpha(): # checks if character is in the alphabet
            empty_key = empty_key + key[i % len(key)] # append characters to empty key
            i = i + 1 # increase integer value by 1
        else: 
            empty_key = empty_key + ' ' # if character is a space or punctuation then add empty space
    return empty_key

def encrypt_decrypt(message_char, key_char, choice='encrypt'):
    if message_char.isalpha():
        first_alphabet_letter = 'a' # assume character is lowercase
        if message_char.isupper():
            first_alphabet_letter = 'A' # assume character is upper, then replace with A

        original_char_position = ord(message_char) - ord(first_alphabet_letter) # difference results in position of char in alphabet
        key_char_position = ord(key_char.lower()) - ord('a')

        if choice == 'encrypt':
            new_char_position = (original_char_position + key_char_position) % 26 # encrypts & loops back around with % 26
        
        else: # if choice == 'decrypt':

            new_char_position = (original_char_position - key_char_position + 26) % 26 # decrypts & loops back around
        return chr(new_char_position + ord(first_alphabet_letter))
    return message_char

def encrypt(message, key):
    cipher = ''
    empty_key = encrypt_key(message, key)

    for message_char, key_char in zip(message, empty_key):
        cipher = cipher + encrypt_decrypt(message_char, key_char)
    return cipher

def decrypt(cipher, key):
    message = ''
    empty_key = encrypt_key(cipher, key)

    for cipher_char, key_char in zip(cipher, empty_key):
        message = message + encrypt_decrypt(cipher_char, key_char, 'decrypt')
    return message

message = input('Enter your message to encrypt here: ')
key = input('Enter your key: ')

cipher = encrypt(message, key) # inputs message and key to encrypt function
decrypt_message = decrypt(cipher, key)# inputs message and key to decrypt function


print(f'Cipher: {cipher}')
print(f'Decrypted: {decrypt_message}')

def choice():
    user_choice = int(input('''
Enter your choice (1 or 2):

1. Encrypt
2. Decrypt

>  '''))
    if user_choice == 1:
        print(f'Cipher: {cipher}')
        print('')
    elif user_choice == 2:
        print('')
        print(f'Decrypted: {decrypt_message}')

choice()