I have a few Uno's and about 5 nanos and several of them have developed the same problem - the board is no longer powered from the USB cable when I plug it in. If I supply 5V to the 5V pin from another Arduino it works though, and I think it also still works if the Vin pin is used to power it. What did I do wrong? I have used up to 12V on the Vin pin to power them occasionally. Should they work fine with 12V ?
Thanks
Its possible you pooched you USB port.
Do you have another computer to try ?
12V has been seen to pooch some Arduinos when not regulated properly or badly connected.
You might have popped the regulator and if you are good with soldering you can swap those unless its taken anything else out.
I thought that when on USB power it doesn't do through the regulator, I thought it switched between Vin and USB depending on which was higher voltage, so it didn't make sense that USB power wasn't working but Vin power was working.