Please try the following:
・For SIM cards: Remove the SIM, gently wipe it with a dry cloth, reinsert it, and ensure Mobile Data is turned on.
・For eSIM: Turn off your device, then turn it back on.
If the problem persists, please contact us through “Post-Purchase Form” on our website’s “Help&Support” page with your SIM card number and several screenshots of your device’s settings.