TMNT Achievement bug?

there is this one achievement its call ''Get your first coin'' i know what it mean but i still didn't get it. I'm on level 11 and i still didn't get that achievement and I've gotten all of the coins in level one. I'm i doing something wrong? is this a Bug? do i have to do a pacific think to get it?TMNT Achievement bug?
Maybe they mean the very first coin you can possibly get in the game. TMNT Achievement bug?
Gold coins not silver.
Yeah I thought it was too but these are special coins only available when you replay the game.To get one, start the game over upon finishing it and you'll get your first coin in seconds.
Go into the trial or challenge modes. The coin you need is there.
replay a mishion you allready beat..

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