Plugin update failed

Hey I was updating the theme and it gave me this error –

Fatal error: Uncaught Error: Call to undefined function vc_set_template_dir() in /home/simplewh/public_html/simplewholesaling.com/wp-content/themes/fortuna/functions.php:422 Stack trace: #0 /home/simplewh/public_html/simplewholesaling.com/wp-settings.php(426): include() #1 /home/simplewh/public_html/simplewholesaling.com/wp-config.php(96): require_once(‘/home/simplewh/…’) #2 /home/simplewh/public_html/simplewholesaling.com/wp-load.php(37): require_once(‘/home/simplewh/…’) #3 /home/simplewh/public_html/simplewholesaling.com/wp-blog-header.php(13): require_once(‘/home/simplewh/…’) #4 /home/simplewh/public_html/simplewholesaling.com/index.php(17): require(‘/home/simplewh/…’) #5 {main} thrown in /home/simplewh/public_html/simplewholesaling.com/wp-content/themes/fortuna/functions.php on line 422

I guess the theme and visual composer dont work.

Can someone help what to do

I tried disabling the theme and plugins but doesnt work