And it goes wrong again since this morning.

My iPhone 8plus comes back to normal tonight. Very interesting. How could this happen?

I've installed iOS 14.5.1 on my iPhone 8 plus and since then, I lost the signal and I don't have data. I have an Android phone, and my sim card works well with it.  I tried many things like: Turn off/on cellular data Turn off/on airplane mode Turn off/on roaming Hard reboot Soft reboot  Reset network setting  Reset all settings Erase all contents and settings ... Same issues Do you have any idea how to fix it?