Welcome to the community @Christophe_QUEVAL!
Can you confirm the command line you are running to restart the server? For example, are you using sudo systemctl start mongod (systemd) as suggested in Install MongoDB Community Edition on Red Hat or CentOS?
It looks like you have followed the instructions to create a seperate nproc configuration from the UNIX ulimit Settings page. If you are using the default systemd installation, you can also specify resource limits within the [Service] sections of service scripts.
Regards,
Stennie