Hey Mr.OhM, this means there is likely a trade ban on your account from Steam. There is nothing we can do from our end. This is question 1 of the FAQ. If it is another reason, please let us know when you find out so that we can update the FAQ, but that is the only thing we know that causes that message.

This is not probem with me. Me friend also have this problem

Do you guys have mobile authentication set up yet?

Yes, but I use it 4 days.

Ok. Once it's been a week, make sure to turn on Confirmation of Trades in your profile settings, otherwise Steam places items in a 72 hour trade hold. Canceling trades during these 72 hours results in a 7-day trade ban.

Ok. Realy thx. I caceled 72 hours trade and I get ban. Thx man.