There are multiple reasons you could be getting no heat. First, the engine may not be getting warm enough fast enough. This could be from a faulty thermostat - sticking open. Second, the heater core may not have flow. You might have a hot hose going in, but a cold one coming out. This could be from a restriction. Third, you may have a temperature blend door motor in the dash failed.
Testing is in order to determine your failure. Good luck!