Fatal Error

Since this morning, my website is down.
My server technical person said that the theme is the cause.

I have the EnfoldVersion: 3.1.3
this the message I have after I activate the theme:

Fatal error: Uncaught Error: Function name must be a string in /home/pumpsan8/public_html/wp-content/themes/enfold/framework/php/class-htmlhelper.php:222 Stack trace: #0 /home/pumpsan8/public_html/wp-content/themes/enfold/framework/php/class-htmlhelper.php(131): avia_htmlhelper->render_single_element(Array) #1 /home/pumpsan8/public_html/wp-content/themes/enfold/framework/php/class-adminpages.php(205): avia_htmlhelper->create_container_based_on_slug(Array, ‘avia_active_con…’) #2 /home/pumpsan8/public_html/wp-includes/class-wp-hook.php(298): avia_adminpages->render_page(”) #3 /home/pumpsan8/public_html/wp-includes/class-wp-hook.php(323): WP_Hook->apply_filters(”, Array) #4 /home/pumpsan8/public_html/wp-includes/plugin.php(453): WP_Hook->do_action(Array) #5 /home/pumpsan8/public_html/wp-admin/admin.php(222): do_action(‘toplevel_page_a…’) #6 {main} thrown in /home/pumpsan8/public_html/wp-content/themes/enfold/framework/php/class-htmlhelper.php on line 222

I reverted back to default WP theme for now, but please let me know what are the steps to fix the issue and be able to use Enfold theme back,
Thanks