Guess the computer's number using functions
There is a classic problem in this condition:

while replay_question != 'y' or 'n':


It always evaluates to True since string n is always truthy.

And, here is a set of code style violations I would work on:


guess variable inside the human_guess() function is unused
keep 2 blank lines between the function definition (PEP 8 - Style Guide)
put the main() function call into under the if __name__ == '__main__': 
the print("Invalid. Enter a number between 1-100 ") is overly indented with 8 spaces, use 4 spaces
you can use a multi-line string for your intro message:

print("""
Welcome to, Guess My Number!
Simply guess the number between 1-100 that the Computer is 'thinking' of!
""")