MiiCoffee Nano Coffee Scale is a capable espresso scale. Here are some the behaviors that might confuse many people. This article explains a lot of details of using MiiCoffee Nano Coffee Scale for making espressos.
To weigh coffee beans or make brewing coffee please make sure you have set the scale in "PR2 manual mode".
To switch mode please double tap the timer button (the button on the left) and you will see PR1 or PR2 starts flashing. And then double tap the timer button again to switch mode.
To weigh espresso dripping from portafilter basket you need to use PR1 espresso mode. In this mode the scale starts timer and weighing automatically when it senses the first drip. Keep in mind that the scale will stop the timer and weighing when the constant dripping stops. So this mode is not good to weigh coffee beans because it can stop weighing.
To charge MiiCoffee Nano Coffee Scale please make sure the main power switch is on (see below photo) and use the regular USB charger that output 5V and 1A. Notice the fast USB chargers might not work because they usually output 12V instead.
If charging is progress you should see a flashing charging icon.
Here is the instruction video.