Check the power connection first. The DC connector must be fully plugged into the Aromax base and the adapter must be plugged into a working power point.
If the unit has power but won't start, the 'on' button light is likely red, indicating it's off. Press the 'on' button until the light turns blue to activate the unit.
If that didn't work: The timer may have elapsed and auto-shut off. Press the 'on' button again to restart it. The selected durations are 15 min, 30 min, 1, 2, 4, or 8 hours.
Heads up: Only use the adaptor supplied with the unit. Using a different one can damage it or prevent it from turning on.