After getting your Carte vitale, as an expat living in France, an account with Ameli.fr will have to be opened. All too often it's too difficult for people who don't speak the language and usually because non-French speakers are going to have trouble calling the CPAM hotline, they will just let it go and sweep it under the carpet. But, it really is important, since that's the easiest place to download the all-important "attestations" to prove that you are covered by the Social Security system in France. If there are any problems that's where you can contact the CPAM in the easiest way. It's also where you can see what's being reimbursed and keep a check on things. Remember the most important thing when you go to see any doctor or do anything (blood tests, ambulance, hospital...), you must show both your Carte vitale and the Mutuelle, top-up that you will have taken out. Sometimes the Mutuelle doesn't make the reimbursement automaticly and if that's the case, and you haven't been reimbursed the first time you go to the doctor's, then the Mutuelle will need to be contacted and told so that they can set it up. Another bit of administration and don't ask me why it doesn't happen automatically, but, they sometimes need to be jimmied along.
Even when you have got your Carte vitale, you may have to call the CPAM to be able to open the Ameli.fr account. They may ask you to send a RIB before it can be opened.
It's a long slog for something so very simply. But, armed with patience, it will get sorted out. It will take a few weeks. You will need an individual email address to be created and to be able to access the internet site for Ameli.fr.