Freshaire by ecoquest air freshener (by 2 users)

I would guess misplaced wire.
Depending on how many and which wires you displaced to accomplish the bulb replacement. I would have to guess that if you did everything correctly and perfectly then the circuit board failed.
My other guess is that if you removed the front panel to circuit board connectors, you may not have reconnected the smaller thin ones on the left in the correct position.

If those check correct and all the other wires are in the correct locations, then there is a repair outfit located through the internet that seems reasonable for approaching for a more involved repair job. The one I looked up had rebuilds available, so you might be able to get a replacement for a better price with your old one exchanged.
If you go this route, just do a web search for EQ air purifier parts/repair.