楽しいことを仕事にするためにした３つのこと

Fatal error: Uncaught Error: Call to undefined function is_plugin_active() in /home/xs114023/hoshi-site.com/public_html/wp-content/plugins/rich-table-of-content/functions.php:519 Stack trace: #0 /home/xs114023/hoshi-site.com/public_html/wp-content/plugins/rich-table-of-content/functions.php(653): rtoc_get_index('\n<p>\xE3\x83\x9C\xE3\x82\xAF\xE3\x81\xAF\xEF\xBC...') #1 /home/xs114023/hoshi-site.com/public_html/wp-includes/class-wp-hook.php(308): rtoc_switch_mokuji('\n<p>\xE3\x83\x9C\xE3\x82\xAF\xE3\x81\xAF\xEF\xBC...') #2 /home/xs114023/hoshi-site.com/public_html/wp-includes/plugin.php(205): WP_Hook->apply_filters('\n<p>\xE3\x83\x9C\xE3\x82\xAF\xE3\x81\xAF\xEF\xBC...', Array) #3 /home/xs114023/hoshi-site.com/public_html/wp-includes/post-template.php(255): apply_filters('the_content', '<!-- wp:paragra...') #4 /home/xs114023/hoshi-site.com/public_html/wp-content/themes/jin/single.php(81): the_content() #5 /home/xs114023/hoshi-site.com/public_html/wp-includes/template-loader.php(106): include('/home/xs114023/...') #6 /home/x in /home/xs114023/hoshi-site.com/public_html/wp-content/plugins/rich-table-of-content/functions.php on line 519