1) If no SIM card is detected, power off your LINKHUB, and reinsert the SIM card, then try again.
2) If a PIN code is required, enter the PIN code, and try again.
3) If no network is available, place the LINKHUB in an area with better signal (for example near a window), and try again.
4) Reboot your LINKHUB, and try again.
5) If the MAC filter function is enabled, make sure your device MAC address is on the whitelist.