A picture that comes up scrambled, inverted or in the wrong colours usually means Nibble has the wrong display driver selected. That is a quick one to fix, as Nibble can switch between the display drivers it supports.
Press and hold the Menu button.
With Menu still held down, press the reset button.
Keep Menu held until the screen shows "Hold Menu button to switch display driver", then release it.
Nibble restarts with a different driver selected, and the picture should now be correct.
If the screen stays completely dark rather than showing a bad picture, this is not the right fix. See My Nibble screen is completely dark, which covers the solder joints to check.
If the picture is still wrong after switching drivers, message us here, or email [email protected], with your order number, a photo of the screen as it looks and photos of both sides of the board, and we will take it from there.