Pressure Plates are not working.

You see, what happened was when I pressed my pressure plate to open a door, it didn't work. The pressure plate didn't actually act as if I was standing on it. So, that's pretty much it.

How to occour:
1. Get the 13w16a Minecraft.
2. Place a pressure plate.
3. Stand on it.
4. Notice that it doesn't ativate, even if you attach it to something.