SIM800C developer board "SIM not inserted"
The print on the PCB and product description at sellers site states it is GSM/GPRS board. The  module on the board comes from SIMCom. This particular SIM800 module seems to have following capabilities as per SIMCom:


Compliant to GSM phase 2/2+
GPRS multi-slot class 12/10
Quad-band 850/900/1800/1900MHz


I think at the best you can only use a 2G SIM card on this board. Any 3G/4G SIM will not work.

Thanks for those images in the problem description, it gave me relevant keywords to search.