possibly because in any of your submission your code matches with someone else code if it happens even in one problem only then also your contest is skipped i guess you shouldn't try to cheat next time

Before updating your rating after the end of the round, for each participant his seed is calculated, that is the place that the participant is expected to take in this competition. Thus, two things are known for each participant — his seed (the expected place) and rank (the actual place). Depending on the difference between these two values, your rating increases or decreases. If the difference is higher, your rating changes more.

You can read more about it here: Codeforces Rating System — Codeforces