I'd authenticate and put in my steam guard code but it would just go back to the login page (steam client would authenticate and show me logged in). In fact, in my case I could not even log in to steam via a browser. I was able to log in to steam from the client but my wishlist was inaccessible, I could not buy games due to the login verification popping up and failing, etc.
In case anyone else is searching the web and finding all the solutions provided didn't work for them, I had a completely separate resolution: I had to remove steam guard and re-add it.
