One line of my family's four lines is affected.

Rebooting the phone does not help. The affected phone sees the network, but shows "No service" error. It seems like some kind of authentication issue?

It's very weird. Been talking to someone else with multiple lines... we'll call them X and Y.

Then I have two lines, J and K.

K and Y have the issue. X and J do not.

K can send and receive texts with X and J, but cannot call them (with or without WiFi calling.)

K and Y cannot text each other.

K cannot check voicemail.

Didn't a lot of certs just switch to a shorter renewal period ?