Team Fortress 2 is not letting me trade. It says, "Your account cannot trade right now". I waited for 6 or 7 days but I still can't trade, what do I do?
This might be due to the fact that Steam was down around the time you were trying to trade. Everything was down, from inventory to servers.
You could try again or submit this question within the TF2 discussion page: http://steamcommunity.com/app/440/discussions/