To successfully scan your dot with any phone make sure that the NFC function is ON and you are tapping the sweet spot with adjusted motion.
When tapping your dot to an iPhone, the sweet spot is right at the top, around the camera.
When tapping your dot to an Android, the sweet tap spot is more in the middle.
Tapping with more motion will help activate the NFC sensor faster, especially for phones that have never come in contact with NFC before.
When tapping to an iPhone X or older the NFC scanner in the control center must be used. *function is available with iOS 14
Note that dot.devices can NOT be scanned if:
the flashlight is ON
the phone screen is OFF
their phone is in Airplane Mode