If this problem happens you may need to try updating the device flash firmware
before you may proceed to hardware troubleshooting.
The solution below shows the sim card circuit on Nokia C6 PCB board which can be used to repair Nokia c6 if insert sim card problem occurred.
Nokia C6 Insert Sim card Repair solution
The Sim card data signals is feeds to the power IC (AVILMA), In tracing this line paths you may need to remove the power IC first and then rework or re-ball it before in-placing it back.
Reheating or re-flowing the IC may fix the Nokia c6 insert sim card problem sometimes, but reworking or re-balling the solder balls is highly advised.