It may be the case with your Samsung Galaxy S6 that this suddenly no longer recognizes the SIM card. This is fact is shown to you on the display in the form of a message. In this case, you cannot do phone calls with your Samsung Galaxy S6 or use the mobile Internet. This is obviously bad and that's why we want to show you here a few tips that will have an effect instantly.
If your Samsung Galaxy S6 no longer detects the SIM card, then:
1. Turn off your Samsung Galaxy S6 and wait about 20 seconds. Then restart the phone.
2.Remove the Sim card by using the tools from the bay and blow into the sim card slot.
3. Check whether the SIM card has any damage, corrosion, etc. on the chip. If so, clean it carefully.
4. Test another SIM card to check whether the cause is the Samsung Galaxy S6 or the SIM card.
Usually Tip 1 already helps to solve the problem with the SIM card and your smartphone.