Diagnosis
That solid red light means the unit has lost its Wi-Fi connection and is stuck in a 'safe mode'. It's a common hiccup, especially after a router reboot or a power blip.
How to Fix It
First, you need to reset its network brain. On the iSmartGate unit, press and hold the small reset button for about 10 seconds until the red light blinks. Let it go, and wait for the light to turn solid white. That means it's ready. Now, open your iSmartGate app, go to the menu, tap 'Add Device', and follow the steps to reconnect it to your Wi-Fi network. It'll ask for your Wi-Fi password again.
If That Didn't Work
The problem might be the power supply. Unplug the small power adapter from the wall and from the iSmartGate unit for a full 60 seconds. Plug everything back in firmly. Watch the light cycle. If it goes green, then red, then finally solid white, you're back in business.
Heads Up
When reconnecting in the app, make sure your phone is on the same 2.4GHz Wi-Fi network you're telling the iSmartGate to use. It can't join a 5GHz network, and your phone jumping to 5GHz during setup is a classic trip-up.