The Scan mode uses NFC (Near-Field Communication) technology. Not all phones are equipped with NFC. If your phone is enabled for NFC, you may need to manually activate it in your phone's settings.
How do I check if my phone has NFC and how do I turn it on?
Android:
Go to Settings > Wireless & Networks. You will either see NFC in that menu, or a More option where you will then find NFC. From there you can toggle it off or on.
You can also contact your phone’s manufacturer to confirm whether this feature is available on your device.
iPhone:
For iPhones XS, 11 and 12, NFC is on by default.
For iPhones 7, 8 and X using iOS 14, you can turn on NFC from the Control Center.
For iPhones 6 and older, the NFC feature is not available.