If you are unable to see a simpleSUM in the Geocene mobile app, first attempt to press its button or tap it with an NFC reader. Detailed instructions can be found here:

Prepare a simpleSUM for Use

For a Dot, hold down the button for 5 seconds. Detailed instructions coming soon!

If the device is still unresponsive, even after pressing its button or tapping it with an NFC reader, you can replace its batteries. simpleSUMs and Dots require alkaline AAA batteries (not rechargeable). We highly recommend using new, fresh batteries from a reputable brand such as Energizer or Duracell.

To replace the batteries: