Why isn't my furnace starting?

We have a Consolidated Industries All Purpose upflow furnace which is not kicking on. We have replaced circuit boards, capacitor and the inducer motor. We also put a new thermostat in. It works fine when running and is very quiet.

After we replaced the thermostat and capacitor, it ran perfectle for about a week, then it kicked off and will not kick back on unless we power it off and back on.

The thermostat still showed heat on.