How can I correct this beer material? I have a beer setup in my blender scene. It's a basic glass shader for the glass containing a fluid mesh with a glass + volume absorption material with a tint.

I don't understand why the fluid is rendering completely black.
Here's a render.



It's supposed to look more like this (froth and bubbles aside):



Here's the fluid node setup:



Here's the glass node setup:



I don't know what's going wrong. I've tried a couple of things.

Thanks for your help in advance. Please let me know if you need more information.

EDIT:
I've upped the light bounces and this is the finished result, thought you might want to see :) (obviously still needs some tweaking)
Even though you have 'Transmission' bounces set to 12 you are capping the 'Max' bounces to 4, meaning it's never doing 12 bounces. Here I have upped the 'Max' bounces to 6 and the liquid started to let light through: 



If you want the liquid to use all 12 Transmission bounces you will have to set your 'Max' bounces to 12 as well.