A problem recently encountered was my brand new Apple iPhone 7 Plus telling me that there was an Invalid Sim Card or Sim not valid, after just one day!
Before marching immediately to your nearset Apple Store, just check that you have done all of the below to save you a trip.
By Rikki Robertson-Brown, posted July 20, 2017
> First of all, ensure that your mobile phone provider hasn't cut you off or suspended your services.
> You should always update your iPhone software to the very latest version of iOS, especially as there are so many security concerns nowadays.
> If you swipe up from the very bottom of the screen, you will see the airplane button pop up or you can go to your settings and turn on airplane mode. Wait for about 10-15 seconds, turn off Airplane Mode and wait for the networks to come back.
> The IT support classic; Restart your device. Now on the older iPhones you could reset by holding both the side and home buttons together but NOW you have to press and hold the side Sleep/Wake button and the DOWN volume button and the screen will go blank and reset. Note that this is a HARD RESET which just means it has refreshed the memory, processor and tempory memory like cache etc, it WILL NOT erase your iPhone.
> You can check to see if there are any carrier settings updates by going to Settings > General > About and wait for about 5-10 seconds and If an update is available, you'll see the prompt popup to select and update them. (This one worked for me)
> I am sure you would have tried this first but if not you can try to remove your SIM card from the SIM card tray and then after some magic puffs of breath, put the SIM card back in the correct way. Ensure the SIM tray is closed completely and isn’t at all loose or sticks out.
> If you have one spare, you could try using another SIM card. If you haven't got one or can not borrow a SIM then you should go to your local phone shop to see if they might have one you cold use as you might need to replace your SIM card.
> After all of the above, if you still see the alert, either go to an Apple Store or contact Apple Support to get it fixed under the warranty or a replacement.