Put your SIM into a friend's phone. If it works there, the problem is your phone. If it doesn't work there, your SIM card is likely dead.
Skin oils or dust on the SIM’s gold chip can block the signal.
In rare cases, the phone itself is the problem. A bent pin inside the SIM tray, a faulty reader circuit, or water damage can make every SIM appear invalid. why does it say invalid sim
Carriers push small updates to help your phone talk to their towers; if these are old, you might lose connection.
If you are seeing this error, it generally boils down to one of three specific problems. Here is the breakdown of what is happening behind the scenes: Put your SIM into a friend's phone
If none of the above works, the SIM may need to be replaced or reactivated. Carriers often replace SIMs for free or a small fee (usually $5–$10).
The most frequent cause. A tiny bit of dust or a slight bump can knock it out of place. Skin oils or dust on the SIM’s gold
If you just switched providers, your phone might still be locked to your old carrier.