Terminals, like mobile phones, will not work if there is insufficient charge in the battery.
If the terminal is connected to the mains via a charging base: try connecting the power cable directly into the terminal: you are looking for a lightning flash through the battery symbol on the top right of the terminal screen.
If this isn’t visible, it indicates a problem with the battery. Remove the back of the terminal and make sure the battery is securely fitted. Hold down the green “Enter” key. If the terminal still doesn’t “power up”, the likely solution is a replacement battery. Customer Service will arrange.
If this still doesn’t solve the issue, a replacement terminal will need to be requested via Customer Support.