Why is my gas furnace not working?

We had our old gas furnace replaced with a brand new one. I noticed the filter needed changed so I did. But I took the panel off as it was still running (as i was able to do with the old one) and now its not kicking on. I believe the panels are in the correct spot. Its a Revolv model. Is this a safety feature that... show more We had our old gas furnace replaced with a brand new one. I noticed the filter needed changed so I did. But I took the panel off as it was still running (as i was able to do with the old one) and now its not kicking on. I believe the panels are in the correct spot. Its a Revolv model. Is this a safety feature that shuts it off if the panel is removed while running? If so, how do I fix it? I tried resetting the breaker then the thermostat and nothing.
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