DIAGNOSIS It's probably not getting power internally. The first thing to check is the simple, often overlooked connection between the base and the main unit.
FIX Let's trace the power path. 1) Unplug the power cord from the wall AND from the socket on the bottom of the purifier's base. 2) Check that the cord is firmly plugged into the base. 3) Now, look at the bottom of the main unit (the part with the fan). You'll see three metal contact pins. Look at the base—three corresponding contact points. Wipe both with a dry cloth to ensure they're clean and free of dust. 4) Carefully re-seat the main unit onto the base, making sure it's aligned and sitting flush. You should hear a faint click. 5. Plug the cord back into the wall. You should immediately see the power indicator light on top glow.
IF THAT DIDN'T WORK Try a different power cord if you have one that fits (it's a standard 'figure-8' or IEC C7 connector). If a known-good cord doesn't work, the issue is internal, likely in the power supply in the base. That's a job for Blueair support.
HEADS UP Always move the unit by lifting the main body, not by carrying it by the top handle with the base dangling. That can strain and damage those internal power connections over time.