Sounds like something might be blocked in the coolant lines.
There should be a gold pipe that runs around the front of the motor from the exhaust manifold (left hand side, near the turbocharger) to a valve body on the intake manifold. At the front of the motor this pipe thickens and has two rubber hoses connected to it. One of these rubber hoses connects to the heater matrix inside the cabin. If coolant isn't flowing through this hose, the matrix inside could be blocked (or the hoses themselves, but more likely the matrix inside).
The other thing to check is whether you have any coolant at all in the system. You could pull the top hose off the radiator and give one of the lower hoses a squeeze. If nothing comes out, you might not have any coolant in the system so you'll need to check for leaks.