Flashing went without any error? (which commands did you use? rebooted in between?)
Then this should have worked, see
https://talk.maemo.org/showpost.php?...83&postcount=6

But I do remember also some ereports of N9 resetting whenever SIM was inserted (might be HW failure?).

Another thread:
https://talk.maemo.org/showthread.ph...hinese+cmt+003

You guys are unbelievable, still jumping in to help!

So I found this article:
https://medium.com/other-oses/awaken...e-a2dd596e540d
...but I found it missing out info here or there, so I switched to this guide and followed it step-by-step:
http://talk.maemo.org/showthread.php?t=82693

I went through the flashing process and I got the CMT error I was expecting. I was cautious enough to check the phone's FW version before flashing: 40.2012.21-3_PR_LEGACY_003, without the word "legacy". So I thought it was the regular Chinese version, but I found the product code and based on the product code it is actually variant 280: 3 SE SE Black 16GB V1 - MR (https://n9.silma.nl/downloads/N9-variant-table-PR13.txt).
So I got the variant 480 FW (as suggested in the article) and the flashed the phone, got the CMT error and then I flashed the CMT only from the variant 003 legacy FW: success!

Then I insert the SIM card and the reception bars are crossed over with a red line and the phone shuts down. I checked talk.maemo.org and read through the threads about this issue: it seems there is no solution!
I can't go back from variant 480, the phone does not let me. So I actually stuck with a phone, for which I don't have the right FW, but even if I had it, I could never use it with my EU SIM cards...

I shouldn't have trusted that ******* I bought the phone from. Oh and btw I disassembled the phone to fix the screen, as it was half way out when the device arrived. I glued it back, no problem there. Then I checked the board: it is missing at least 3 screws, and there are some bended covers for the chips and some Chinese stickers here or there. There is some staining on the SIM tray, so either phone was overheating (would explain the broken and dry glue on the screen), or got washed out, but it would have been shortened, so maybe just got overheated. It is a refurbished phone, which I think never worked properly.
Man, do I feel dumb?

So it seems it goes to the drawer next to my N900 and some other Nokias and Lumias I have collected over the years.