Press these keys individually in the mentioned order do not press them together:
After successful reset keyboards which can connect up to three devices should have the LEDs blinking on F1, F2, and F3 keys.
There may be few reasons you want to reset your logitech keyboard, something is not working as expected, the keyboard is powering on but not functioning at all or you are reselling your keyboard.
In my case the LED over the f2 key was blinking on my Logitech PopKeys and it was not connecting to any device. After successful reset I turned off the keyboard and then turned it back on. This resolved the issue and the keyboard started working properly.