almera n16 stereo issue

[Roastyduck]

fitted a new stereo to my n16 almera a few weeks back, all has been good.. sub and amp in the boot with some 6x9 in a fabricated parcel shelf.. amp has been a bit dodgy past few days going into protection mode, only real cure was disconnecting the signal wire and reconnecting it which was all well and good until screwing it up i shorted against the side of the amp by accident....

stereo went off, amp went off.. managed to trace it back to the blue wire to the radio which supplies volts when the ignition is on.. voltage just doesnt get to it... now what?

any idea how far i need to go back to trace this wire or what the issue with it could be...

radio fuse not blown
fuse box fuses all appear good unless theres one i cant see.
everything else works fine
12v socket that only comes on with ignition still works fine.