There are two things I would do...
First, turn off your device, remove your SIM card, and just clean off the SIM contacts with a lint-free cloth - just give them a good wipe down, then re-insert your SIM card. It should be a very snug fit, and make sure the card is inserted correctly and the contacts are good and solid, there is no wiggling when the SIM card is installed. It's possible the SIM card just wasn't making a clean connection.
Power the phone back up and see what happens.
If it's still a no-go, I'd take it back to Orange and get a fresh SIM card. They should be able to transfer the contacts to a new SIM for you in the shop and verify it works before you leave.