No air coming out of vents

What is your question?

When I turned my heater on this morning, nothing came out I tried all the settings, tried it on low, medium, high...nothing. Nothing comes out at all in the front. But when I turn on the rear heat, it works, but it blows cold air. I just changed the blower motor resistor about 3 weeks ago. Anybody know what it could be? I need it fixed because I live in Minnesota so I need my HEAT!