For mine (2021 MiC LR) when it was delivered in March and had the same issue as the
@Mcs3 decribes, the mobile service guy _did_ just replace the SIM card in it. He told me there were quite a few cars in that batch that had non-functioning SIM cards put in them at the factory and it wasn’t picked up before delivery, so he had a fair pile of replacement (Telstra) SIMs in a rubber-banded pile in his car for doing exactly that fix. This was in the first batch of MiC cars, so it just felt to me at the time like a “teething problem” with the new factory and new delivery centre (Chatswood in Sydney). Strange for the same thing to be still getting all the way to customers if that’s what it turns out to be. I almost hope it is a one-off problem with a suddenly failed board in @Mcs3‘s car rather than a non-functioning SIM still being able to be in the car and not tested and picked up as a possible known issue in Tesla’s delivery preparation by now.