I bought this switchbot on amazon.de: https://amzn.to/2XVHUpJ
I opened the button plastic on the top and check the battery, everything is okay. I press that small button in the corner of this device and the green light flashed. I thought that it should work fine.
I install the software on Samsung J3 smart phone. I rechecked all options, bluetooth on, everything but the button doesn't connect with phone no matter what I tried.