Please kindly follow these steps to bind it again:
1. Turn off Bluetooth in your smartphone and then turn it back on
2. Turn off Petfon APP and then turn it back on
3. Tear off the yellow films under your controller and tracker and fully charge them both.
4. Open PETFON App(the APP might ask you if you permit Petfon to use your Bluetooth, location,microphone,camera and send you notifications. Please always click "YES". Since these options are all important in your use. If you clicked "no" for any of them, you could delete Petfon APP and download it again)
5. Please go to Petfon APP▶Menu▶Devices▶"+"▶Controller&Tracker. and try scanning controller and trackers again.