I privately bought a white N9 (still in awe of its beauty :P).
The seller said he had no problems with it, the last time it was used (years ago). He tested it for me & came back saying it would not recognise a SIM card.

I bought it anyway expecting broken 'sim pins'. By looking down the port it looks fine to me (comparing with working & broken pin phones).
I have looked through all the threads with title keyword 'SIM'.
It's a Chinese phone. I've tested with 2 SIMs / cleaned with eraser / sandwiching paper / swapping SIM trays.
IMEI etc are all indicated on "About Product" page (with/without SIM).

I've "Zeroize flashed" with Australia firmware -> expected errors -> used Chinese firmware for CMT -> indicated successful (MD5 correct).
Still not recognising SIM (now indicates "Emergency calls only) & NO error messages.

I've read that the battery can be a cause. Does long battery life cancel this out?

Should I open up the phone? Ideas?

Edit: Just tried to flash with only the Chinese firmware, which failed (with SIM).