Fatal error: Uncaught Error: Call to undefined function is_plugin_active() in /home/xs132271/akihabara-bc.jp/public_html/wp-content/plugins/rich-table-of-content/functions.php:519 Stack trace: #0 /home/xs132271/akihabara-bc.jp/public_html/wp-content/plugins/rich-table-of-content/functions.php(1380): rtoc_get_index('<p>&gt;2023\xE5\xB9\xB4\xE3...') #1 /home/xs132271/akihabara-bc.jp/public_html/wp-includes/class-wp-hook.php(324): rtoc_switch_mokuji('<p>&gt;2023\xE5\xB9\xB4\xE3...') #2 /home/xs132271/akihabara-bc.jp/public_html/wp-includes/plugin.php(205): WP_Hook->apply_filters('<p>&gt;2023\xE5\xB9\xB4\xE3...', Array) #3 /home/xs132271/akihabara-bc.jp/public_html/wp-includes/formatting.php(3965): apply_filters('the_content', '&gt;2023\xE5\xB9\xB4\xE3\x81\xAB\xE3...') #4 /home/xs132271/akihabara-bc.jp/public_html/wp-includes/class-wp-hook.php(324): wp_trim_excerpt('&gt;2023\xE5\xB9\xB4\xE3\x81\xAB\xE3...', Object(WP_Post)) #5 /home/xs132271/akihabara-bc.jp/public_html/wp-includes/plugin.php(205): WP_Hook->apply_filters('', Array) #6 /home/xs132271/akihabara-bc.jp/public_html/wp-includes/post-template.php(436): apply_filters('get_the_excerpt', '', Object(WP_Post)) #7 /home/xs132271/akihabara-bc.jp/public_html/wp-includes/embed.php(1011): get_the_excerpt() #8 /home/xs132271/akihabara-bc.jp/public_html/wp-includes/theme-compat/embed-content.php(101): the_excerpt_embed() #9 /home/xs132271/akihabara-bc.jp/public_html/wp-includes/template.php(812): require('/home/xs132271/...') #10 /home/xs132271/akihabara-bc.jp/public_html/wp-includes/template.php(745): load_template('/home/xs132271/...', false, Array) #11 /home/xs132271/akihabara-bc.jp/public_html/wp-includes/general-template.php(206): locate_template(Array, true, false, Array) #12 /home/xs132271/akihabara-bc.jp/public_html/wp-includes/theme-compat/embed.php(18): get_template_part('embed', 'content') #13 /home/xs132271/akihabara-bc.jp/public_html/wp-includes/template-loader.php(106): include('/home/xs132271/...') #14 /home/xs132271/akihabara-bc.jp/public_html/wp-blog-header.php(19): require_once('/home/xs132271/...') #15 /home/xs132271/akihabara-bc.jp/public_html/index.php(17): require('/home/xs132271/...') #16 {main} thrown in /home/xs132271/akihabara-bc.jp/public_html/wp-content/plugins/rich-table-of-content/functions.php on line 519