Fatal error on mobile phones only

So I’m getting this error, but on mobile phones only. It works fine on my laptop.

I activated JetPack’s mobile theme. It gave me this error. So I then deactivated it. But the error is still there.

All of my plugins are updated. I tried deactivating all of them. That didn’t help.

Fatal error: Uncaught Error: Call to undefined function businessx_cd() in /home3/learnfun/public_html/norwichrotaryevents/wp-content/plugins/businessx-extensions/inc/customizer/theme-mods.php:852 Stack trace: #0 /home3/learnfun/public_html/norwichrotaryevents/wp-includes/class-wp-hook.php(286): businessx_extensions_final_inline_css(”) #1 /home3/learnfun/public_html/norwichrotaryevents/wp-includes/class-wp-hook.php(310): WP_Hook->apply_filters(NULL, Array) #2 /home3/learnfun/public_html/norwichrotaryevents/wp-includes/plugin.php(453): WP_Hook->do_action(Array) #3 /home3/learnfun/public_html/norwichrotaryevents/wp-includes/script-loader.php(2231): do_action(‘wp_enqueue_scri…’) #4 /home3/learnfun/public_html/norwichrotaryevents/wp-includes/class-wp-hook.php(286): wp_enqueue_scripts(”) #5 /home3/learnfun/public_html/norwichrotaryevents/wp-includes/class-wp-hook.php(310): WP_Hook->apply_filters(NULL, Array) #6 /home3/learnfun/public_html/norwichrotaryevents/wp-includes/plugin.php(453): WP_Hook->do_action(Array) #7 /home3/l in /home3/learnfun/public_html/norwichrotaryevents/wp-content/plugins/businessx-extensions/inc/customizer/theme-mods.php on line 852

Please help. I’m running a major fundraiser, and I need this site to work.

The page I need help with: [log in to see the link]