DIAGNOSIS The 2.4 GHz Wi-Fi setup is failing. This model does NOT support 5 GHz networks. The most likely cause is your phone being on the wrong network band or being too far from the router during setup.
FIX Force your smartphone to connect to your 2.4 GHz Wi-Fi band. This often requires temporarily disabling 5 GHz on your router or using a separate SSID. Stand close to your router with the purifier. In the app, select 'Vital 100S' (not just 'Vital'), and ensure the purifier's display is showing the Wi-Fi icon blinking.
IF THAT DIDN'T WORK A common glitch is the purifier's Wi-Fi module getting stuck. Perform a hard reset: unplug the purifier, press and hold the Power button on the unit for 20 seconds, then plug it back in. The lights will cycle. Try setup again from scratch.
HEADS UP Once connected, the purifier only needs Wi-Fi for remote control and scheduling. It will run /auto modes just fine without an active connection.