If you have different number of plies along the length of the blade, then the thickness will not be constant. You should get a linearly changing thickness similar to the model I showed in another post:
Make sure you don't disable the ply drop-offs. Don't check the boxes in the image above.
Make sure the number of plies is different along the length of the blade and that the thickness is varying:
If the thickness is constant, then something is wrong in your model and layup.
If you follow the manufacturing process of the blade in ACP, you should be okay. In real life, which layer is put in the mold first? Then, this first layer should be applied in ACP. Which layer is put in the mold second? Do the same in ACP.
Let me know how it goes.