Steam Trade Issue

If you cancelled a trade that was already in the 24-hour or 72-hour wait period, it results in an automatic 7 day trade suspension. I never heard about the 3-day option.
In these cases it is safer to let the trade go on, and just trade it back after.

Did you cancel the trade when it was on hold?

Yep, just as talgaby says. I have a trade on hold, so I can copy-paste you the official text: "Cancelling outstanding trades will begin a 7 day trade cooldown."

From Steam:

Trades that are on hold have been accepted by both parties and will complete by the date specified on each trade offer. If you did not make these trades or wish to cancel them, you can do so by cancelling all outstanding trades (both those on hold and pending). Cancelling outstanding trades will begin a 7 day trade cooldown.

I've canceled individual trades on hold without issues. I thought the trade cooldown only applied if you clicked the "cancel all outstanding trades" button.

7 days ..there is warning about that ;) you need to read more before doing something :D
http://prntscr.com/9k00sw

hate new steam rules

wonder what 2 do if i dont have smartphone, dont use steam ?

Thanks Obama, i mean, gaben... This happened to me last week, because i was sending trades and 2 guys accept the offer, i had to cancel (both of it, cant cancel just 1) because i didnt want to lose both cards... stupid mobile shit