I’m making a function that return the sum of the all number in the FizzBuzz list. I thought it would be fine but not working. In Python

The result is 0
It should be 60 if I type 15 but not. I don’t know why but n_numlist is empty. Where is my mistake?
I cannot find it!! Is there someone who can find? Please help me!!

#This is my code:

def to_fizzbuzz(number):
if number % 15 == 0:
    return 'FizzBuzz'

if number % 3 == 0:
    return 'Fizz'

if number % 5 == 0:
    return 'Buzz'

    return str(number)
    # return i

def main():
N = int(input())
# this list concludes "FizzBuzz", "Fizz" or "Buzz"
fblist = ()
for number in range(1, 10**6):
    result = to_fizzbuzz(number)

# the list up to N
n_list = fblist(0:N)
# this list contains only numbers and up to N

n_numlist = ()

for s in n_list:
    if s.isdigit == True: