Diagnosis
This is usually a power supply issue. The MinusA2 has an external AC adapter, and those can fail or get loose.
How to Fix It
Check that the power adapter is firmly plugged into both the wall outlet and the port on the back of the purifier. Try a different wall outlet to rule out a dead socket. If possible, test with another 24V DC power adapter that matches the specs.
If That Didn't Work
If you're sure power is reaching the unit, there's a small chance the internal fuse or control board has blown. You'll need to contact Rabbit Air support for service.
Heads Up
Never try to open the unit or repair the internal electronics yourself—you'll void the warranty and risk electric shock.