It is possible to revive my Arduino Leonardo (mini beetle) board? I have this board:



It has the atmega32u4 chip.

I have updated its code several times, and used it without issues for several months. Today, while updating (using Arduino IDE) it started to throw some errors. At the end it said that the checksum didn't match, so I repeated again few more times with the same behavior until it reported "Uploaded" without errors. I used for few minutes and it was working as expected. Then, I had to do another update and the same happened (checksum didn't match). However this time I got to the point in which it was no longer detected by the OS (Ubuntu), and no LED is turning on.

Whenever I connect it to the USB port, I can only see in the logs:

usb 1-9.4: new full-speed USB device number 9 using xhci_hcd

However /dev/ttyACM0 is not longer created.

I'm trying to use avrdude to reset it, but it is reporting:

avrdude: ser_open(): can't open device "/dev/ttyACM0": No such file or directory

which make sense as /dev/ttyACM0 doesn't exists. So, what are my options? Is there anything I can do to make it work again?

UPDATE

I didn't realize that this board has a reset marked as "RES". Following Juraj recommendation I bridged RES and GND. The LED marked as "SDA" turns ON after I release the contact and I can read in the logs:

[1212051.679205] usb 1-9.4: USB disconnect, device number 22
[1212058.532030] usb 1-9.4: new full-speed USB device number 23 using xhci_hcd
[1212058.621972] usb 1-9.4: New USB device found, idVendor=2341, idProduct=0036
[1212058.621982] usb 1-9.4: New USB device strings: Mfr=2, Product=1, SerialNumber=0
[1212058.621988] usb 1-9.4: Product: Arduino Leonardo
[1212058.621994] usb 1-9.4: Manufacturer: Arduino LLC
[1212058.622933] cdc_acm 1-9.4:1.0: ttyACM0: USB ACM device



Which I think its good news. However, it seems ttyACM0 becomes available for few seconds. I was able to upload the Blink example into the chip and I can confirm its working because its blinking. Still the ttyACM0 disappears after few seconds. 

Output of avrdude -c avr109 -p atmega32u4 -P /dev/ttyACM0 :

Connecting to programmer: .
Found programmer: Id = "CATERIN"; type = S
    Software Version = 1.0; No Hardware Version given.
Programmer supports auto addr increment.
Programmer supports buffered memory access with buffersize=128 bytes.

Programmer supports the following devices:
    Device code: 0x44

avrdude: AVR device initialized and ready to accept instructions
Reading | ################################################## | 100% 0.00s
avrdude: Device signature = 0x1e9587 (probably m32u4)
avrdude: safemode: Fuses OK (E:FB, H:D8, L:FF)
avrdude done.  Thank you.
Probably you have overwritten your Bootloader.
Connect MOSI, MISO, SCK and RESET to an ISP-Programmer and flash the file
Caterina-LilyPadUSB.hex
to it.
There are lots of tutorials on the net how to use a spare arduino as an ISP-Programmer.