To use an opening sensor you need to make sure that:
- Have a 2nd generation 1Control LINK device (to distinguish it from the 1st generation LINK, the 2nd generation LINK has a white case)
- LINK and the sensor must be within 15 meters (even less if there are obstacles).
- Update LINK to the latest version available by going to Settings-->Manage your devices-->Select LINK-->More options-->Update your device.
- Update the 1Control app to the latest available version.
Attention!
Remember that each sensor must be connected to an access, so to connect the sensors, press the round button on the back of the sensor (it will light up briefly and then turn off, it's normal) then go to: Settings-->Manage your devices-->Select ONLY-->Select the access you want to monitor-->Select "Opening sensor"
In the case of a door opening sensor, make sure it has power: remove the plastic tab from the battery compartment. 
In the case of a gate or garage opening sensor, make sure that the sensor is turned on: press the round membrane button on the sensor several times
Finally, move the opening sensor and its magnetic contact closer and further away from each other to check their operation and the change in status.
If the problem persists:
- Make sure that there are no obstacles between the LINK and the sensors that could prevent correct communication between the two devices.
- Please make sure LINK is updated to the latest version.
You can check it this way:- Open the 1Control app
- Go into the app settings
- Open the "Manage your devices" section
- Select LINK
- Press "More options"
- Go to the "Update your device" section and follow the instructions shown
- Make sure the LINK antenna is screwed in securely and pointing upwards.