Uno rev3 stuck on uploading

Hello,
I've using my uno rev3 board for few months, it used to work properly, now when I power it up, the built in LED doesn't flash anymore (it just lights up and stay like that), and I can't upload my sketches it's either stuck on uploading, or showing an error:

Sketch uses 1888 bytes (5%) of program storage space. Maximum is 32256 bytes.
Global variables use 188 bytes (9%) of dynamic memory, leaving 1860 bytes for local variables. Maximum is 2048 bytes.
An error occurred while uploading the sketch
avrdude: ser_open(): can't open device "\\.\COM3": Le fichier spécifié est introuvable.


Problem uploading to board.  See http://www.arduino.cc/en/Guide/Troubleshooting#upload for suggestions.
Exception in thread "Thread-56" java.util.ConcurrentModificationException
	at java.util.LinkedList$LLSpliterator.forEachRemaining(LinkedList.java:1239)
	at java.util.stream.AbstractPipeline.copyInto(AbstractPipeline.java:481)
	at java.util.stream.AbstractPipeline.wrapAndCopyInto(AbstractPipeline.java:471)
	at java.util.stream.ForEachOps$ForEachOp.evaluateSequential(ForEachOps.java:151)
	at java.util.stream.ForEachOps$ForEachOp$OfRef.evaluateSequential(ForEachOps.java:174)
	at java.util.stream.AbstractPipeline.evaluate(AbstractPipeline.java:234)
	at java.util.stream.ReferencePipeline.forEach(ReferencePipeline.java:418)
	at cc.arduino.contributions.libraries.LibrariesIndexer.rescanLibraries(LibrariesIndexer.java:127)
	at cc.arduino.contributions.libraries.LibrariesIndexer.setLibrariesFolders(LibrariesIndexer.java:106)
	at processing.app.BaseNoGui.onBoardOrPortChange(BaseNoGui.java:682)
	at processing.app.Base.onBoardOrPortChange(Base.java:1297)
	at processing.app.Editor$DefaultExportHandler.run(Editor.java:2179)
	at java.lang.Thread.run(Thread.java:745)

Did I break it or something? Also when I plug it I can open the serial monitor and send something and the RX flashes.
Thank you.

Select the correct COM port from tools -> port menu. The port number assigned will depend on which USB port the arduino is plugged into and/or what other devices are connected at the time, and the IDE will remember the one you selected. But if you then plug it into a different usb port it may have a different COM port number, so the port that the IDE remembers doesn't exist. Which is what that error says.

If tools -> port is greyed out, either you have a driver problem (ruled out if it used to work on that computer and you haven't updated the OS or messed with drivers since it last worked), your USB cable is bad (there has been a plague of bad USB cables, I think someone is distributing low quality ones that fail frequently with clone arduino starter kits), the USB port has failed, or the usb-serial adapter on your board has failed (this is most common on genuine boards and clones using the 16u2 - for whatever reason, it seems easier to damage if something goes wrong on the power rails.)

I kept the same usb port and the same cable, which was working well before, I think because I did some dodgy wirings... :frowning: Thanks