Sim Lock "Unknown Error"

I have just inserted a new sim card into my Z3C running Slimm 1.7, and it requested an unlock code. I used the following sequence to get some data -

1. Turn on the phone without sim card
2. Type *#*#7378423#*#*
3. Select Service info
4. Select SimLock

But all the entries say "Unknown error"

What can I do?

from xda-developers http://ift.tt/1S6yHvc
via IFTTT