RNS-D - won't unlock using its Security Code

[mik15]

i bought a used RNS-D unit which was taken off a 2001 S8, it came with the Security Code, it is in a very good condition, all good, up until i hooked it up, as it doesn't unlock when the Security Code is typed in.

Initially i thought that maybe the seller being a scrapper mixed up the Code with another unit, so i double checked and Audi has confirmed the code he sent me.

Does anyone have any idea why does it do it?

I've tried coding it, even though it was already properly coded coming from an S8, i did it anyway but with no results.

I am kind of stuck at the moment and any idea would be appreciated....

L.E. - the error code i get on the display is now: SAFE PIN NOT CONNECTED.