Here are the steps to re-calibrate the Ingenico isc250 screen:
  1. Press and hold CLEAR and – (minus) simultaneously on the iSC250 payment terminal to reboot it.
    Retail Base screen  Retail Base screen
  2. When the iSC250 reboots and the grey Retail Base screen appears, press 2  6  3  4 and ENTER. You will only have a short moment for this step. If you miss, start back at step #1.
  3. Press + 9 7 for Menu.
  4. Press 0 for Manager Menu.
  5. Press 0 for Telium Manager.
  6. Press 3 for Initialization.
  7. Press 2 for Hardware.
  8. Press 4 for Calibration.
  9. Press + for Yes.
  10. Press Green.
  11. DO NOT touch the device until is says Calibration Successful.
  12. Press Red until you get back to the home screen.