cryptography.fernet.InvalidToken problem with cryptography

Getting this error when trying to run this:

  File "Test Files.py", line 502, in decryptdefault
decrypted = fernet.decrypt(d)
  File "/usr/lib/python3/dist-packages/cryptography/fernet.py", line 74, in decrypt
timestamp, data = Fernet._get_unverified_token_data(token)
  File "/usr/lib/python3/dist-packages/cryptography/fernet.py", line 92, in _get_unverified_token_data
    raise InvalidToken

cryptography.fernet.InvalidToken

FYI dk variable is defined with key (default key)

dk = 'niwaXsYbDiAxmLiqRiFbDa_8gHio15sNQ6ZO-sQ0nR4='
# Decrypts the file with default key
def decryptdefault(inclufile):
    Key = dk

    fernet = Fernet(Key)
    readfile = open(inclufile, 'rb')
    d = readfile.read()
    readfile.close()

    # Decrypts and puts it into the text
    if readfile != "":
        decrypted = fernet.decrypt(d)
        decrypted = str(decrypted).replace('b'', '', 1)
        decrypted = decrypted[:-3]
        return str(decrypted)

Edit: I added the key for those who asked

Answer

I have found out, through trial and error with the same project later down the line, that you need to turn your key into something like this key = b'niwaXsYbDiAxmLiqRiFbDa_8gHio15sNQ6ZO-sQ0nR4='

The main difference being the key is encoded in a utf-8 format and is now readable by Fernet and doesn’t return that error. Here is a function that uses Tkinter, Fernet, and os to actually decrypt my file.

# Propriatary method of encrypting files
def decrypt(self, file):
    with open(file, 'rb') as readfile:
        contents = readfile.read()

    self.title(os.path.basename(file) + ' - SecureNote')
    # self.textbox is a variable inside of the class I am using for my window
    self.textbox.delete(1.0, tk.END)

    if contents != "":
        # getword retur
        Key = bytes(getword('Key:', 1), encoding="utf-8")
        fernet = Fernet(Key)

        decrypted = fernet.decrypt(contents).decode('utf-8')
        self.textbox.insert(1.0, str(decrypted))

        del Key
        del fernet
    else:
        pass