If your iOS widget doesn't display data, most likely you need to activate the Widget with a station.
Go to the AirVisual app settings (the wheel in the top right corner) and then go to widget to select a station or a Node. Next (very important!), you need to quit the settings by pressing "Back" in the top left corner in order to save the settings. After that step, the widget should update with the latest information.
We also found a glitch affecting some iOS10 users that can't display data in the widget. You need to allow the AirVisual app to accept notifications. During the installation, a pop up question is asked, answer "Yes" then. This glitch will be fix in our next iOS version.