Error in recognizing arduino on ubuntu 20.04

I just bought an ARDUINO MICRO and it looks it is recognized by the system since it shows on /dev/ttyS0. The sketch I wrote compiles without error, but when I try to upload I get:

If I press the reset button, as suggested, after starting the loading process, I get

Arduino: 1.8.13 (Linux), Board: "Arduino Micro"

Sketch uses 4026 bytes (14%) of program storage space. Maximum is 28672 bytes.
Global variables use 149 bytes (5%) of dynamic memory, leaving 2411 bytes for local variables. Maximum is 2560 bytes.
An error occurred while uploading the sketch
avrdude: ser_open(): can't open device "/dev/ttyACM0": Permission denied

Using the verbose output, I get:

Arduino: 1.8.13 (Linux), Board: "Arduino Micro"

Sketch uses 4026 bytes (14%) of program storage space. Maximum is 28672 bytes.
Global variables use 149 bytes (5%) of dynamic memory, leaving 2411 bytes for local variables. Maximum is 2560 bytes.
PORTS {/dev/ttyACM0, } / {/dev/ttyACM0, } => {}
...
PORTS {/dev/ttyACM0, } / {} => {}
PORTS {} / {} => {}
...
PORTS {} / {} => {}
PORTS {} / {/dev/ttyACM0, } => {/dev/ttyACM0, }
Found upload port: /dev/ttyACM0
/home/gigiux/src/arduino/hardware/tools/avr/bin/avrdude -C/home/gigiux/src/arduino/hardware/tools/avr/etc/avrdude.conf -v -patmega32u4 -cavr109 -P/dev/ttyACM0 -b57600 -D -Uflash:w:/tmp/arduino_build_442878/pushLED.ino.ino.hex:i 

avrdude: Version 6.3-20190619
         Copyright (c) 2000-2005 Brian Dean, http://www.bdmicro.com/
         Copyright (c) 2007-2014 Joerg Wunsch

         System wide configuration file is "/home/gigiux/src/arduino/hardware/tools/avr/etc/avrdude.conf"
         User configuration file is "/home/gigiux/.avrduderc"
         User configuration file does not exist or is not a regular file, skipping

         Using Port                    : /dev/ttyACM0
         Using Programmer              : avr109
         Overriding Baud Rate          : 57600
avrdude: ser_open(): can't open device "/dev/ttyACM0": Permission denied

avrdude done.  Thank you.

Problem uploading to board.  See http://www.arduino.cc/en/Guide/Troubleshooting#upload for suggestions.

It looks like a system error more than a board’s issue. What would be the problem? The troubleshooting list does not give a proper solution for this issue since it does not mention access denied to port…

Thank you