Serioux S51 MP4 player firmware request

[Janos]

Hi guys.
I have a Serioux MP4 player like this:


I haven't used it for a while and when i started it, i got only a dark screen.
If i connect it to the computer, it is detected as a mass storage device. I can copy files to it, etc.

Here is my info taken with ChipGenius:

Description: [G:]USB Mass Storage Device(S51 MP4 PLAYER)
Device Type: Mass Storage Device
Protocal Version: USB 2.00
Current Speed: High Speed
Max Current: 400mA
USB Device ID: VID = 071B PID = 3203
Serial Number: USBV1.00
Device Vendor: RockChip
Device Name: ROCK MP3
Device Revision: 0100
Manufacturer: S51
Product Model: MP4 PLAYER
Product Revision: 1.01
Chip Vendor: RockChip
Chip Part-Number: RK2606~RK2706

Although ChipGenius says it is a RK2606~RK2706, i am not sure. I opened it and it seems to have a Rockchip Nano (RKNANO) inside.
Now thing is that i cannot find a firmware for this player. I tried to contact the manufacturer but useless. I have asked from a friend another, working player which is exactly the same. I tried to extract firmware from it with the rkusb.tag method, tried aldo renaming the file to different names but i cannot show the hidden partition to read the firmware.
Can anybody help me with the firmware, or an idea, how to read it?

Thanks in advance,

Janos