Doing all the quests & actually clearing all the mines are 2 different things. If you did indeed clear all the tiles in each mine, check your inventory & verify whether you have (at least) 50 green bow ties. If you do, try clearing the gsme cache/ cookies & refreshing the game as that sometimes helps the game register the Achievement.
If still no joy, contact SUPPORT via the button under the game settings wheel (upper corner of the game window.)
PS: Because players often mistake the Achievement for the Treasure, thought I'd mention that Treasure Pieces don't count as tiles, so one can complete each mine without having gotten all the pieces. If you by chance this is what you meant, click on the Treasure in your Museum to open the info window. Then click the icon to see where the missing piece is.