What am I missing

Question

I made a credit card validator. It passed 6 out of 7 test cases. The one that failed it hidden. I can't figure out what I'm missing. The program uses the luhn formula which I broke into separated callable functions to modify vector components.
https://code.sololearn.com/cBLhr6Jwm9V5/?ref=app

Answer 1

Thank you Bob_Li. You helped me spot the error. Plus I liked your solution

Answer 2

observations:
since you are using namespace std, you could leave out the "std::" from your code to reduce clutter.

you are not taking advantage of c++ libraries, which would make your code much simpler.

not everything have to be broken up to functions. It's an unnecessary complication for this task

Answer 3

//Malachite modify this part:
// function to minus 9 from any digit larger than 9 in the vector.
vector<int> subNine(vector<int> &vect){
int temp;
for(int i = 0; i < vect.size(); i++){
if(vect[i] > 9){
temp = vect[i] - 9;
vect[i] = temp;
}}return vect;
}