Hello, this problem happens occasionally to the nanos and it is that the internal power on reset does not work well when feeding it with only 5v through the Vin, keep in mind that Vin is connected directly to the internal regulator and you need a couple of more volts so that this regulator a stable voltage of 5v. You have three ways to try to fix it:
1- connect an electrolytic capacitor of about 10uF between the Reset pin and GND, with this you add an external power on reset that takes longer than the internal one, (it is as if you press reset a little later).
2- power by Vin with at least 6.5 / 7v
3-If you are sure you have 5V, feed it through the 5V pin.
If either of these doesn't work, discard the plate and use it for testing only.
Greetings.
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