It’s always been like that. When the sim loses connection, it can revert back to ‘offline mode’. You’ll be notified about this with a small pop up window (bottom right of the screen I believe) that doesn’t stay on screen too long, so it can be easy to miss.
When that happens you need to re-enable the online functionalities under general options → data.
This is not the same as the annoying big connection lost / reconnected popups you get in the middle of your screen that lock out your controls for a bit. I think those are for when the sim can’t connect to those online services it needs without losing internet connectivity.