Plugin facetwp disfonctionnement

Bonjour,
Je recherche quelqu'un capable de me faire fonctionner un plugin de recherche interne au site,
Le plugin qui semble disfonctionner c'est facetwp
code erreur:
PHP Fatal error: Uncaught Error: Call to undefined method stdClass::set() in /var/www/html/artistesenligne/wp-content/plugins/relevanssi/lib/search.php:1241\nStack trace:\n#0 /var/www/html/artistesenligne/wp-content/plugins/facetwp-relevanssi/facetwp-relevanssi.php(106): relevanssi_do_query(Object(stdClass))\n#1 /var/www/html/artistesenligne/wp-includes/class-wp-hook.php(298): FacetWP_Relevanssi->search_facet(false, Array)\n#2 /var/www/html/artistesenligne/wp-includes/plugin.php(203): WP_Hook->apply_filters(false, Array)\n#3 /var/www/html/artistesenligne/wp-content/plugins/facetwp/includes/class-facet.php(348): apply_filters('facetwp_facet_f...', false, Array)\n#4 /var/www/html/artistesenligne/wp-content/plugins/facetwp/includes/class-facet.php(96): FacetWP_Facet->get_filtered_post_ids()\n#5 /var/www/html/artistesenligne/wp-content/plugins/facetwp/includes/class-ajax.php(156): FacetWP_Facet->render(Array)\n#6 /var/www/html/artistesenligne/wp-content/plugins/facetwp/includes/class-ajax.php(97): FacetWP_Ajax->get_preload_data('wp')\n#7 in /var/www/html/artistesenligne/wp-content/plugins/relevanssi/lib/search.php on line 1241

Merci
cdt