I can't fix my network problem. Why Japan firmware is outdated among the other version. I have seen other version have Android Pie update and some simcard fix update. But this Japan version is too slow for a progress. I started to get disappointed to my device. Please do some checking here. I choose Asus because the developer here is Updated to what we need. But this Japan version sucks about the update.
Note: I'm done to all troubleshooting but still it can't fix. My only chance is an update.
Are your firmware version currently on JP-18.104.22.168?
Please also help me to remove the SIM card, restart the device then re-insert the SIM card for a check.
I would suggest you can try to reset the network settings.
(settings> system> reset options> reset wifi, mobile & Bluetooth)
Does this problem appear if you use a sim card of another carrier?
Could you show me SIM status screenshot when you encounter this problem?
(settings> system > about phone > status > sim status)