The phone world is activated and the card is not displayed.

The reason is the service problem of the operator. Sometimes, even if the SIM card is correctly inserted into the telephone world, the mobile phone cannot display the card because the service of the operator is faulty or not activated. You can insert the SIM card into other mobile phones, but you can't display the card on other mobile phones, so it's the operator's problem and you need to contact the operator to confirm the solution.