My Epson Expression Photo XP760 switch lights up but won't switch on when the button is pressed. It was working fine until I got a warning that there was a problem with the black ink cartridge. I removed and reinstalled the cartridge and the printer went through the charging process and then switched off. If the mains supply is unplugged and the reconnected the printer goes through the usual start-up sequence but the screen does not light up and the power button just flashes. Pressing the power button then has no effect. Any ideas ?