I hate when they give you that message! It really annoys me, because it makes it seem like just because you did good, they will not reward you. I am not sure if you really did get the "maximum score", or if it is just a glitch, because I know somtimes you get that message as a glitch Congrats on getting the trophy your first time, though!
It stinks when they do that because maybe you spent a really long time on that one game of eager beaver and you do really good and you want your kinzcash and you don't get it.