Arduino won't show up in serial port at all despite working perfectly fine??

Development Tools IDE 1.x
1

I ran an arduino uno overnight in order to use it as a trigger for a switch. The arduino is using an LCD shield and runs the code appropriately, but I can't connect to it in order to upload new code. When plugged in it's evident that everything is fine with the arduino, but none of my computers (pc and mac) were able to find it in the serial port despite it working completely fine yesterday. I tried rebooting both computers but no luck. It ran all night plugged in via USB, I'm not sure if that'd really do anything but I figured I'd mention that.

I can still connect to my Mega and my other 2 Uno's but this Uno which ran overnight won't connect

Is there anything I haven't thought of or realized? I'd imagine this is a common problem but what can I do about it?

2

power on your arduino device using external power supply.

when using external power supply dont use USB cable.

for a debugging code you will get USB to TTL converter. USE it tx & Rx pins to obtain serial out.

There is no harm debug Arduino unless you do not connect shield/ or motor driver to Arduino boards.