I've had a similar problem some versions before. I could solve it by installing the specific modem for my carrier:
Options -> Xperia Parts -> Modem Switcher Activity -> Switch Modem
There you have to select the modem for your provider and reboot.
Hope it works for you too
Thanks for solutions.
Actually, Japanese carrer not exist there
So I can't enable VoLTE...
But 4G can enable.(it requires some steps... enable 3G data network, then switch to LTE. Please see atatched movie.)
Anyway, thanks for good solutions!