If you have put that green tile in A1 then it definitely will not work. The tiles on the A sheet work differently, and have a different format, to all other tiles. You need to put it on a B-E sheet. If you look at the tiles in the default sets you will see the differences between them.
EDIT
It might work on A5, depending on what it is (is it a floor tile?), but A1, A2, A3, and A4 are quite different.