I am being copyright noticed

I have been copyright warned for music

“ckotty-Game Loop 1-ckotty”, sound recording administered by: 11:12
AdRev for a 3rd Party
"ckotty-Corporate Loop 6-ckotty", sound recording administered by: 0:48
AdRev for a 3rd Party

Why is this happening

You used an un-authorized music in that video. Better delete that video before you get a strike, mate.

But I have heard other videos with the music, so why do I get punished

Because you were unlucky!

The official statement is;

"You have our permission to create lets play videos. Please include a link to our website http://www.greenheartgames.com/
However we reserve the right to revoke, without prejudice, this permission at any given point in the future.

Please note that the in-game music is not licensed for use in videos so please disable the music or use your own."

But other people don’t read that
http://www.youtube.com/watch?v=Fni1PaZoeVE

That.

Yes, and others who haven’t read it will have what happened to you happen to them sometime soon. My advice? Take the video down, replace the music with something you’re allowed to use. You can find some good stuff here: http://incompetech.com/music/royalty-free/, and it’s pretty lenient about how you’re allowed to use it. Just be sure to read whatever restrictions that may come with it.

Privited it for now

You are allowed to leave the music on if you plan to talk over the top. but you will get flagged if the music is the sole audio source. This is because the same laws which prevent you from simply using the music for your own ends without asking permission, also tend to have exceptions to allow for review and critique.