I don't have an FG621-EA modem (e.g. most recent LTE6 devices) nor SIM locking enabled to know. But...I saw this in the release notes for 7.13.3 that seem to indicated this may problem may be fixed:
*) sms - fixed SMS inbox for FG621-EA modem (introduced in v7.13);
Statistics: Posted by Amm0 — Fri Jan 26, 2024 2:00 am