Python Morse Code Translator
General Style
Your translation dict uses a keyword and lower case letters.
Consider writing constants with upper-case letters and giving them expressive names like MORSE_CODES = {...}.
According to PEP 8, functions should be named using snake_case. CamelCase is reserved for classes:
outputMessage → output_message, def Encrypt(...) → def encrypt(...), etc.
Performance
Using the Get_Key function is not very performant, since it performs a linear search of the dict. Just reverse the translation dict once and then use it:
MORSE_ENCODING = {
    'a': '.-',
    'b': '-...',
    ...
}
MORSE_DECODING = {value: key for key, value in MORSE_ENCODING.items()}

...

        temp = MORSE_DECODING[letter]

Handling errors
Currently the Encrypt function silently skips all non-translatable characters. Consider Throwing a ValueError() instead to indicate, that invalid input was provided:
def encode(message):
    &quot;&quot;&quot;Encodes a string into morse code.&quot;&quot;&quot;

    code = ''

    for index, char in enumerate(message):
        try:
            code += MORSE_ENCODING[char.lower()]
        except KeyError:
            raise ValueError(f'Char &quot;{char}&quot; at {index} cannot be encoded.')

        code += ' '

    return code[:-1]  # Remove trailing space.


def decode(morse_code):
    &quot;&quot;&quot;Decodes morse code.&quot;&quot;&quot;

    message = ''

    for index, sequence in enumerate(morse_code.split()):
        try:
            message += MORSE_DECODING[sequence]
        except KeyError:
            raise ValueError(f'Cannot decode code &quot;{sequence}&quot; at {index}.')

    return message

Correctness
Your Encrypt function currently always returns a trailing space. You can avoid that by returning output[:-1].
Terminology
Converting from morse code to text back and forth is not really an encryption in its sense. You might want to rephrase {en,de}crypt with {en,de}code.
Globals
Using global variables like outputMessage can have nasty side-effects when the program is used as a library. All the code below the def Play_Sound function should go into a def main() function that you can invoke via
if __name__ == '__main__':
    main()

At the bottom of the unit.