I will reply in English as this is an English speaking forum @Laetitia254
Yesterday our government announced that France is now on the quarantine list. This means all but essential travel to France such as holidays is not advised and all visitors must quarantine for two weeks on their return.
I wasn't sure by your post if they cancelled after or before your check in.
The guests may well be able to claim the cancellation under Airbnb's EC policy for COVID. Airbnb would be likely to uphold this if they do as our Foreign Office advice is against all but essential travel because of the rise in Covid cases in France.