Why alpha of my shader not working?

hi, so my fragment shader is not working as expected as usual, here I simply set output as transparent green:

btw, the image of this sprite is a tilescource.

while my other shaders (on sprite with normal atlas) works fine. so did I miss up some settings?

Yes you miss something , which is in defold making alpha channel does not happen only by making the alpha channel to zero , it do like this :
Color.xyzw = colour.w *colour,
Read for example the model.fp you will find in the fragment shader a comment saying what I write it here