Diagnosis
This is a common Wi-Fi setup failure. The most likely cause is an incorrect network band or signal interference during the handshake.
How to Fix It
Follow this exact sequence. Ensure your phone is on a 2.4 GHz Wi-Fi network. Disable mobile data on your phone. Power cycle the purifier. In the Coway IoCare app, delete the device and start a fresh registration. Hold the Wi-Fi button on the purifier for 5 seconds until the light blinks rapidly. Complete the in-app prompts without switching screens.
If That Didn't Work
Your router's security settings may be incompatible. Temporarily disable any advanced firewalls, MAC filtering, or AP isolation on your router. Complete the setup, then re-enable your security settings. The connection will persist.
Heads Up
The Airmega 400 does not support 5 GHz networks. It will not connect if your phone is on a 5 GHz band, even if your router broadcasts both. Verify your phone's connection in Wi-Fi settings before setup.