I am also receiving the same message suddenly this morning, I've removed the sim card and cleaned it with a cloth reset the phone and it is not working
To @sunshine1: Sorry for the very late reply! If you still need help with this matter, please send me a private message including your phone number and PIN. We need that information, as it's very possible we may need to help you with placing a replacement SIM card order.
To @Wyndsol: Since it's very likely we may need to place a replacement SIM card order for you as well, I'll also need you to send me your account's phone number and PIN through a private message.
At your service!
A post I saw from a customer service agent in another thread appears to have worked at this time (at least the card isn't saying invalid for longer then 10 minutes) after rebooting in airplane mood and updating the PRL
Thanks! Your collaboration is highly appreciated, as this will help others find a way around this issue!
If you need assistance with anything else, don't doubt to let us know.