One last tip: Before you leave home, always check that your SIM card is active and properly seated. A two-second glance could save you from a morning of no service and unnecessary panic.
If you just switched providers, your phone might still be locked to your old carrier. why does it say invalid sim
This is the quickest diagnostic. If the SIM works in another device, your phone’s reader or software is likely the issue. If it doesn’t, the SIM is faulty or deactivated. One last tip: Before you leave home, always