I am writing this in hope for finding the solution.
I have arduino Mega 2560, it was all working by using it from external power of 12V. Next day, I again powered it up but it didn't work. I again tried to connect it to laptop to perform re-programming but all failed. error message is saying no port detected . in tool menu, port is greyed. in device manager, there is no sign of Arduino neither unknown or other devices. but whenever i just plug it in laptop, RX, TX and LED13 are always lit, when I press Reset button, LED13 flashes once, then happen nothing.
i replaced it with Arduino Uno R3, firstly it was working and I uploaded same program, inserted into my project, then again it is stuck. LED13 of UNO is always lit, no port is detected in laptop when i plug it in with laptop.
I am awfully stuck. I have to submit my project. Days are passing but my project is incomplete.. Your suggestion would be highly favorable.