Always return false in python outright, it is true

I am writing a program in python that take some string and test it through some condition

1. the first 2 characters in the sting must be letters

2 . the steer must be maximum of 6 characters and at least 2 characters

3 . Numbers cannot be used in the middle of the string; they must come at the end. For example, AAA222 would be an acceptable … ; AAA22A would not be acceptable

4 . The first number used cannot be a ‘0’.”

5 . [‘ ‘, ‘,’, ‘;’, ‘-‘, ‘_’] thos characters are not allowed

this is my code so far

def main():
    plate = input("Plate: ")
    if is_valid(plate):
        print("Valid")
    else:
        print("Invalid")


def is_valid(s):
    total = is_N_1(s) + is_N_2(s) + is_N_3(s) + is_N_4(s) + is_N_5(s)
    if total  == 5:
        #print (total)
        return True
    else:
        #print(total)
        return False


def is_N_1(s):
    if len(s)<7 and len(s)>3:
        return 1
    else:
        return 0

def is_N_2(s):
    if s[0:2].isalpha():
        return 1
    else:
        return 0

def is_N_3(s):
    for i in s:
        if s[-1].isalpha() and i.isnumeric():
            return 0
        else:
            return 1

def is_N_4(s):
    t = []
    for i in s:
        if i.isdigit():
            t.append(i)

    if len(t)<=0:
        return 1
    else:
        if t[0] == '0':
            return 0
        else:
            return 1

def is_N_5(s):
    not_allow =[' ', ',', ';', '-', '_']
    for i in s :
        for _ in not_allow :
            if i == _:
                return 1
            else :
                return 0
main()

this is the input that give an error in the output

1 . input of "CS50" 
    expected "Valid", not "Invalid\n"

2 . input of "ECTO88"
    expected "Valid", not "Invalid\n"

3 . input of "NRVOUS"
    expected "Valid", not "Invalid\n"

can any one take a look at this and tell me what I did wrong, I stack for 2 hours and I did not find the solution?

>Solution :

Below is how to check the string in s one by one for not allowed characters within not_allow. I think that just fixing this part will solve it.

def is_N_5(s):
    not_allow =[' ', ',', ';', '-', '_']
    for i in s :
        if i in not_allow:
            return 0
    return 1