iPod classic working and charging, but not showing up on Mac or Windows

Hi,

I just bought an iPod classic on eBay to use it in my car (it has an old iPod plug).

I charged the iPod with a wall charger and all went fine. The iPod has some music in it and it works. If I plug it into the car, the radio plays the music on the iPod.

However, I cannot have a PC or a Mac recognising it, let alone using iTunes to change the music.

I have tried many solutions, such as:

- reboot (6 seconds menu and selection down)

- reset (12 seconds menu and selection down)

- diagnostic (6 second menu and selection down, then selection and << down)

- disk mode (6 seconds menu and selection down, then selection and play down): in this case it goes to disk mode and says "it's ok to disconnect"

- change USB cable (I have two cables - it is possible that both are broken, but it would seem unlikely to me - both works when I charge the iPod)

- change USB port

- try a PC (Windows 7) and Mac (Air and Macbook)

- try other solutions, such as this: https://www.freemyipod.org/wiki/Restore_iPod_without_iTunes (but the terminal says "DFU device not found")

If I go on info it says:

- 27,8 GB

- version 1.3

- format: Windows

When I plug/unplug it from a PC or Mac the screen lights up and it seems charging (although not showing the charging icon).

In short, it looks like a functioning iPod, that recharges and interacts with the radio in the car, but it won't show up in the computer.

Do you have any suggestion?

Thank you

Giacomo