To check if your sensors and home hub are online please:
Tap the hamburger menu (3 lines) at the top left of the screen
Go into the “Devices” page
Within the app, all the devices (sensors and home hub) will have a green rectangle on their right to flag them as online. If the rectangle is grey, it means they are offline and you will need to investigate further to understand and fix the issue.
The devices that are directly plugged into a power socket will have the label “online” or “offline” depending on their status.
The devices that work with AAA batteries, will have the label “offline” or the percentage of battery that remains.