vectra stereo not working/safe mode?

i own a vauxhall vectra 2003 diesel, stereo (cdr 2005) this morning i disconected the battery,, when i conected it again my car stereo doesnt work, nothing is coming up on my display to say if its in safemode/locked or not,,, ive tried holding in the (AS) button till i hear a beep, prompting me to enter the code, also tried holding AS then turning radio on while holding AS,, also tried turning ignition on radio off,, ignition on holding AS then turning radio on,,,, but still no beep,, i need help!!!!! i have also checked the fuses