Please check if the power cord is securely connected to the air purifier, and also the wall outlet or extension cord.  

In many cases, the power cord was not fully plugged in to the air purifier.  Or, in some cases, the connection between the air purifier and the outlet is loose.

You may also want to check if the outlet you are plugging into is working or not -- try another outlet too just to confirm if it is really the outlet or the air purifier.

Lastly, please check that the HEPA filter is properly fitted into the filter chamber.  The Air Purifier will not switch on if the HEPA filter is not properly secured.  

Disconnect the power by unplugging the purifier from the outlet, and then plug the power cord back into the outlet.  All button functionality should return.

Auto Mode is only available when the air purifier can react to air quality readings from the SensorPod.  Please check that the SensorPod is plugged-in and that its light is solid.  The radio light on the purifier will blink if the air purifier is not responding to the SensorPod.

Check that the air purifier is in the same room and powered-on.  If it is, you'll need to follow the pairing procedures in the manual.

To pair your TruSens with the SensorPod please see image below: