This means your hosting company or server administrator has disabled one or PHP functions that are used by PSN. Usually they do this in an attempt to tighten security, perhaps after a flaw has been found in an old or poorly written plugin. PSN requires a fully functional PHP environment to work properly. PHP with arbitrary functions disabled is not fully functional. You should ask your hosting company to consider removing the block on those functions, particularly parse_ini_file, or at least provide an exception for PSN. PSN does not use parse_ini_file in an insecure manner. Disabling that function does not increase security.
If your hosting company insists on continuing to block functions, you should consider switching to a new host that provides a complete PHP environment.