If your sensors or magnets are mounted on a door or window (or door/window frame) that is wrapped or made of metal, this can interfere with the magnetic field of the magnet. This can also cause the sensors to intermittently work days later.
To test if your metal door or window is interfering with the operation of the sensor, we recommend removing the sensor and magnet and testing the sensor away from any metal (for example, try holding the magnet and the sensor in your hand. Hold the magnet close to the proper side of the sensor, let the magnet touch the sensor then pull the magnet away to see if it shows the status change on your timeline and you should hear the chime sound from the Iota or gateway. Mounting the sensors with a spacer under them that is not conductive (Plastic, 2- sided tape, wood, or foam, etc.) will help situate them away from the metal when they are mounted.
The abode classic door/window sensors offer a wider gap between the magnet and sensor which will usually work better on metal doors.