Logitech K780 Frequently Asked Questions Manual page 30

1. Open Settings and click Bluetooth.
2. Tap on the Logitech device you want to connect to from the Other Devices list.
3. The Logitech device will be listed under My Devices when paired successfully.
Upon pairing, the LED light on the Logitech device stops blinking and glows steady for 5
seconds. The light then turns off to save energy.
 +Unifying devices not detected after macOS 10.12.1 Sierra update
We are aware that after updating from macOS 10.12 Sierra to macOS Sierra 10.12.1, Logitech
Options software does not detect supported Unifying devices on some systems.
To fix this issue, unplug the Unifying receiver and then plug it back into the USB port. If
Logitech Options still doesn't detect the device, you may also need to reboot your system.