How Can I fix my RD4 Player in my Peugeot 407 HDI?

Please does any one know how Ican fix the RD4 cd player in my car (Peugeot 407).
I travlled abroad and my battery went flat before I came back, I fixed a new battery, all other system works but my stereo wont work neither not higligthed on the main control screen. it is not asking for any code, it ejects and admits CDs but not playing or responding to any audio selection or audio key function. And it was working fine and nice before I travlled.
Please any idea of what I can do please.