Diagnosis
The power cord is likely not fully connected to the unit, or a safety interlock is not engaged due to improper reassembly.
How to Fix It
Verify physical connections. First, check that the power cord is firmly plugged into the outlet. Second, and most critical, ensure the cord is fully inserted into the DC power input jack on the back of the purifier. It must click in securely. Third, confirm the top cover is correctly aligned and fully pressed down until it latches on all sides.
If That Didn't Work
You may have triggered the internal tilt sensor. Unplug the unit. Place it on a completely level, stable surface. Rock it gently from side to side to reset the sensor. Plug it back in after 30 seconds.
Heads Up
The unit has a safety switch that prevents operation if the top cover or front panel is not correctly installed. Double-check all covers are flush and latched. A gap of even 1-2mm can prevent startup.