Greetings JL - its a little tricky on the new beetle - its a drain that comes out on the engine side of the firewall (passenger)- there is a small flap in the insulation that you have to lift up to access the drain flap. Have a really good look & you will find it. If the insulatuion gets stuck it will stop the valve venting. Pull the flap up & clean & check the valve.

Good luck!