How to check your device status from the app
Go to Settings > Meters and view the status of each meter
Known issue: Sometimes the meters can show the wrong status temporarily depending on how often your router cycles Wi-Fi clients. Go to the now tab and find the offline meter graph, if there is still live data showing the device is actually online, even though the app mentions it to be offline.
How to check your device Online status on the device
Wi-Fi P1 meter: Green = OK, Red blinking: Offline
Wi-Fi Energy Socket: Green = OK, Red blinking = Offline
Wi-Fi kWh meter: Signal bars on display = OK, No signal bars = Offline
If there is no data showing in the 'now' screen. This means one or more devices are currently not connected to your Wi-Fi. You can check the app for the last known Wi-Fi signal strength percentage at Settings > Meters > 'Your offline meter' > Wi-Fi > ''name'' %. If the signal strength is below 50% you might experience temporal offline states. If the signal strength is below 20% your device will be offline often.
If you are having signal problems you might try to reposition your Wi-Fi router for better coverage. This can be done by rotating your Wi-Fi router, or repositioning your router.