project euler #1 help

Question

hey guys, can someone pls explain why my answer is not correct?

https://code.sololearn.com/c4PUoCz1xJ3C/?ref=app

Answer 1

Could you please explain the concept of your program ?

Answer 2

More elegant way for your task
https://code.sololearn.com/c1EIdcA19192/?ref=app