We suggest plugging Palette™/P+™ into the power supply for all reasons except for updating the firmware. In the case of updating firmware, please ensure that your Palette is plugged into your computer via the USB cord and unplugged from the power supply.
The risk of plugging in Palette via USB and the power supply simultaneously is that, with high-powered PCs, this can sometimes fry the board. This is very rare but can occur in some instances. If this did happen, your Palette would likely not be functional at all (e.g. the screen wouldn't turn on when you plug it in its power supply). To diagnose this, simply plug in Palette and see if the screen turns on and displays the menu as usual.
If you have any questions, send us a message at firstname.lastname@example.org.