If you have the situation that you have flashed the box, but after that, you have no access to repair the box with the network, and serial port. And your display stays on No ca found, or Error and the push button method failed. Than it can be that the serial port chip has been damaged. The only option then is to replace it. But be sure that your serial port from your pc is working, also that the DB9 null modem rs232 cable is good.