As title said, never trade offer sent me(inv opened) at all even though it showed like "in seconds you will get a trade offer, accept it within3 min".
And soon my credit was gone ( equivalent tf2 keys.I pulled out. and now my credit is restored ), but actually there's no trade offer to me from bot.
Edit: I found my credit is not equivalent between deposit tab and withdrawable tab.

Every 1min bot tries to send me a trade offer, whether my inv open or not, seems it's failed.
(I opened my inv more than at least 20min)