Diagnosis
The tip-over switch is stuck in the triggered position. This is a mechanical safety device inside the base.
How to Fix It
Unplug the heater. Pick it up and firmly tap the bottom of the base against your palm a few times. You should hear a faint click. This resets the pendulum switch. Set it down on a perfectly flat, level, hard surface. Plug it in.
If That Didn't Work
The impact may have physically damaged the switch or its wiring. You'll need to open the base housing to inspect. Look for a white plastic box with a metal pendulum. Ensure it moves freely and the wires are connected.
Heads Up
This heater must sit level. Thick carpet or uneven flooring can cause a false tip-over trigger. Always place it on a hard, flat surface.