The SIM card can be a very common culprit when you think there is a Verizon outage. These tiny chips can move around, lose contact with the pins, or sometimes even get dirty or damaged.
Apple ditched the ditched the physical SIM card slot in favor of the eSIM ... Truphone, Ubigi, Verizon Wireless, and Visible. Absent are other carriers such as Google Fi, Consumer Cellular ...