Can't upload sketch, LED not working

Hello Everyone,

I am relatively new to Arduino and have a project I need to work on that involves the Nicla Sense ME.

The problem I am having currently is that I can't upload any sketch on the board. The LED doesn't flash when I upload the sketch, even though arduino IDE tells me that it uploaded successfully.

I can see the COM port under device manager, I can see the board info under Tools->get board info, even the NRF Connect tool on my pc detects the bluetooth on the board and connects.

I checked if just maybe the LED is defective by uploading a sketch that sends data over the COM port, but nothing is sent. Could this be a bootloader issue? And if so, how can I reset it?

Thankfully I have another spare board, which still works, but I want to figure out the issue on this one before I continue.

If this is the wrong category for these kinds of issues, I apologize in advance.

Hi @ismarh. If you upload this "Blink_Nicla" example sketch, do you get a blinking green LED on your Nicla Sense ME board?

#include "Nicla_System.h"

void setup() {

void loop() {

No, the LED doesn't blink while programming is finished, as usual, and it also doesn't blink afterwards.

It might help to know that I have been trying out PlatformIO instead of the usual arduino IDE, so I have a feeling that the bootloader is bricked. I see that you need specific programmers to program arduino boards, and obviously the hex file. Is there somewhere a guide how I can do this with the Nicla Sense ME?

I want to just write what fixed the issue at the end, because I managed to get it working again.
The scary looking option "burn bootloader" did the trick in the end. Just doing that made the Nicla Sense ME perform like usual again.

I was trying out Platform IO, and maybe there was a bug in the way it compiles the data there, or maybe I even unplugged the cable, or bad connection, in the middle of a compile. From the Arduino IDE, I picked "burn bootloader" in the end, because I was sick of searching for solutions for days. It immediately made the LED blink in blue, which is the default color when it is booted up, and compiling and uploading the "Blink Nicla" sketch worked, resulting in a blinking green LED.

I hope this helps someone else who is too afraid to click "burn bootloader" on their new expensive Arduino board!

I'm glad to hear you were able to restore your Nicla. Thanks for taking the time to share your findings!