Hello Michal,
Usually, as long as your caisse primaire d'assurance maladie (CPAM) knows that you left France, your rights are automatically closed and you can not access your online account anymore.
If you need to submit documents, it will only be possible through post to the address of your local CPAM that you will find on ameli.fr, section "Adresses et contacts".
If you need help and want to check your file, you can contact the CPAM’s English or French Advice Lines.
More information in the following topic: How to call the French Health Insurance Advice Lines?
Have a nice day.
