Arduino UNO upload problem

I have a small problem: it's been several months since I had not used my Arduino and now during the upload, it shows me the error.

avrdude: Version 6.3-20171130
Copyright (c) 2000-2005 Brian Dean, http://www.bdmicro.com/
Copyright (c) 2007-2014 Joerg Wunsch

System wide configuration file is "/Applications/Arduino.app/Contents/Java/hardware/tools/avr/etc/avrdude.conf"
User configuration file is "/Users/**********/.avrduderc"
User configuration file does not exist or is not a regular file, skipping

Using Port : /dev/cu.usbmodem14221
Using Programmer : arduino
Overriding Baud Rate : 115200
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 1 of 10: not in sync: resp=0x00
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 2 of 10: not in sync: resp=0x00
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 3 of 10: not in sync: resp=0x00
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 4 of 10: not in sync: resp=0x00
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 5 of 10: not in sync: resp=0x00
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 6 of 10: not in sync: resp=0x00
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 7 of 10: not in sync: resp=0x00
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 8 of 10: not in sync: resp=0x00
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 9 of 10: not in sync: resp=0x00
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 10 of 10: not in sync: resp=0x00

avrdude done. Thank you.

Problème de téléversement vers la carte. Voir http://www.arduino.cc/en/Guide/Troubleshooting#upload pour suggestions.

I have tried everything. Reset during upload, etc., but still show the error.

I do not understand. In addition, the LED "L" remains lit permanently, perhaps a program that runs continuously?

In addition, I can not even burn the bootloader, boot sequence so I have no way.

Do I have to buy a new Arduino completely?

-- INFORMATIONS SYSTEME --

OS: Mac OSX El Capitan 10.11.6 (J'ai testé sur un autre mac doté de la même version) sur MacBook Pro Retina de fin-2012 (j'ai testé sur l'autre mac qui est lui un MacBook Pro de mi-2009)

-- INFORMATIONS ARDUINO --

Version Arduino IDE: Dernière (1.8.6, téléchargée aujourd'hui (27/08/18).

Carte: Elegoo Arduino Uno R3 (équivalent à Arduino UNO R3)
Programmeur: (aucun)

Code du logiciel: Blanc (void setup{}; void loop {})

[X] Câble d'origine du kit acheté
[X] Arduino n'étant branché à rien

Thank you in advance!

Problème de téléversement vers la carte. Voir http://www.arduino.cc/en/Guide/Troubleshooting#upload pour suggestions.

So, did you?

You are using the latest release of the IDE. Sometimes the error you are receiving is an indication of a bad installation. Can you try an older version? Try reinstalling the IDE.