@BravoMike31 

Yes, you can use a common USB cable to reset it. Resetting steps are the same as the steps of using serial port.

https://www.tp-link.com/en/support/faq/2124/

You have to download a driver for the USB cable:

https://www.tp-link.com/en/support/download/tl-sg3428mp/#Driver

@Somnus Thank you for your reply. I have done these already, but without success.

The problem now is that even i press "any key" to stop autoboot, the boot continues.

I have try more than 20 times, with 2 different Pcs

The message "Press any key to stop autoboot : 1" appears for less than a second and pressing any keys the terminal ignores them

Nest step is to try again without all Ethernet cables from switch, so to be free from any load.

Any other idea, is always helpful !!

kind regards

e.a

Unfortunately the switch is faulty and is going to be checked and replaced.

Thank you for your help !

e.a