You reset by a SMS code.
A little backstory. I got this issue during the summer sale. I was trying to trade some cards and couldn't get notifications to show up, no errors no warnings, no nothing. So I reset the authenticator suggested by some users. Now I have to wait 15 days, trading cards will expire before then. I got locked because their app wasn't working and now I have to wait 15 days. I'm not a big card collector but this was the only time I level up my profile. I know this pointless and meaningless crap but I want to bludgeon to death some overweight CEO now.