ramlef, All the firmware I have are already in the firmware download section. I would say the firmware you have loaded is for a player that has nVol+ amd Vol- buttons. You could try loading the firmware into Waterlily and going to the System Keys tab and setting the keys as follows:
Key1=Play
Key2=Menu
Key3=Prev
Key4=Next
Key5=Null
Key6=Null
Key7=Record
Key8=Null
Key9=Null
Key10=Null
Key11=Null
Key12=Null
Hold=Off
This is how the buttons are configured on my Nano clones.
If that does not work then you will have to keep looking for firmware that suits your player.
You can download Waterliliy
HERE