Update: I emailed internetinthecar.vodafone.com. They replied with 2 days and said
If a modem suddenly says there is no sim card inserted, it could mean there is a little bit of dirt in the sim holder or the sim card has been dislodged. At your convenience, please locate your sim card using the attached image and give it a wipe with a clean dry cloth. Reinsert the sim card and it should start working normally again.
I did this but no different. Then I noticed the box was unticked in settings for the car to be a modem. Reticked and everything is working. I wonder what happened to cause the box to be unticked?
Good result and good to know Vodafone get back to customers.
SIM failure
Have you recently had a service or any dealer appointment involving need for the car to be put on diagnostics? Mine was same after service and I thought the 24gb 3 sim had been exhausted. Same solution as you found. They also managed to change the stored key profiles too, very helpful
XC40 D3 Inscription Pro Auto in Denim Blue with Convenience, Xenium and Intellisafe pro packs plus smartphone integration , tinted rear windows and spare wheel.