FortiGate Next Generation Firewall utilizes purpose-built security processors and threat intelligence security services from FortiGuard labs to deliver top-rated protection and high performance, including encrypted traffic.
Article Id 196133
This article describes the 3 different SIM card detection states on the FortiGate 30E-3G4G and what to do if there is an error.

In order to determine the state, one of the following commands can be run:
# diagnose sys lte-modem sim-info
FortiGate-30E-3G4G # diagnose sys lte-modem sim-info
LTE Modem SIM card information:
IMSI: IMSI123456
Country: <Country>
Network: <Mobile Network Name>
# diagnose test application lted 20
FortiGate-30E-3G4G # diagnose test application lted 20
The following are the 3 different states:
- QMI_UIM_CARD_STATE_PRESENT          <----- Indicates a good SIM card is physically detected and able to be read.
- QMI_UIM_CARD_STATE_ABSENT            <----- Indicates no SIM card is physically detected.
- QMI_UIM_CARD_STATE_ERROR             <----- Indicates a SIM card is physically detected, but cannot be read. This is primarily caused by either a bad SIM card or a SIM card that doesn’t make proper contact in the SIM slot.

The following are a few steps to do when 'QMI_UIM_CARD_STATE_ERROR' is appearing:

1) Eject and reinsert the SIM card.

When doing so make sure the SIM status appropriately cycles to ABSENT when the card is removed.

2) Power cycle the modem.

In some cases, there is an issue temporarily reading the SIM card that rebooting the modem will correct:
# execute lte-modem power-off
# execute lte-modem power-on

3) Use a good quality SIM adapter.

Often the error status can be caused by loose contact of the SIM card with the SIM slot and can be seen with some nano to micro SIM adapters. It’s recommended to not use a ‘frame only’ style SIM card, but instead to use a ‘one sided’ style adapter where the smaller SIM is inserted into the adapter.
This helps to secure a better fit/connection.

4) Test a Different SIM card.

If none of the above options work the SIM card may be defective or unable to be read by the modem. In this case it’s advised to test using another SIM card.