Was it exactly max amount or "Max Bet"? Because I see mine is still working though I don't really use it when betting as my bet is not too huge.
Can you clarify? I took a screen shot as a sample because it appears in my account.

It just means clicking that will place a maximum possible bet on that market. Most bookies have a max limit that calculates the max risk they are allowed to accept (because otherwise they will not be able to pay out if too many hit).
True and I understand what you are saying, I was just trying to answer on @tebo question and I want him to clarify if his question was about the max bet.
Trust me, most of us will never hit that limit so clicking that button just means putting all your balance on it. Try it;)
Never did that AFAIR.