Pressing the power button does nothing, no display on the screen.
Replace the AA batteries in the back of the device.
Confirm that all batteries are correctly placed in the battery compartment of the device.
Securely connect the AC adaptor or car adaptor to both the device and the power source.
The picture displayed on the screen is non existent or incorrect and pressing the power button has no response.
Disconnect all power supplies (batteries and adaptor), and then reconnect all power supplies. Remove the cartridge, cleaning it if necessary, and then re-insert it into the device.
It is impossible to select the correct icon on the screen.
To recalibrate the touch screen, turn the device OFF and hold down the "Home" button, the "Question mark" button, and the "Sound/Speaker" button at the same time while turning the device back on. Then follow the steps displayed on the screen.