Fwd: Cellphone can't detect sim card

Hi! I have built 2 units of simtrace hardware recently. All the components came from digikey, I used the bom list from git. The PCBs are electrically tested. When I connected it to the pc, simtrace application can communicate with the device and I can debug it via the FTDI connection. The problem is, when I connect it to a cellphone, cellphone can not detect a sim card. Simtrace can detect vcc on, vcc off and rst signals from the cellphone however, cellphone can not detect the sim card. I used several different cell phones and sim cards. I also checked the connection between the cellhpone and simtrace. Couldn't find a problem. May I kindly request your help to solve the problem? Thanks,