“Causing a fatal error on your site”

Hi there,

I’ve received the following email from WordPress and I can’t seem to see what the problem is.

WordPress version 5.3
Current theme: Edge (version 10.2.1)
Current plugin: Custom Fields WooCommerce Checkout Page (Premium) (version 1.2) PHP version 7.1.33

Error Details
=============
An error of type E_ERROR was caused in line 11995 of the file /home/flooringsolution/public_html/wp-content/plugins/woo-checkout-regsiter-field-editor-premium/freemius/includes/class-freemius.php. Error message: Uncaught Error: Call to undefined function get_blog_list() in /home/flooringsolution/public_html/wp-content/plugins/woo-checkout-regsiter-field-editor-premium/freemius/includes/class-freemius.php:11995
Stack trace:
#0 /home/flooringsolution/public_html/wp-content/plugins/woo-checkout-regsiter-field-editor-premium/freemius/includes/class-freemius.php(12064): Freemius::get_sites()
#1 /home/flooringsolution/public_html/wp-content/plugins/woo-checkout-regsiter-field-editor-premium/freemius/includes/class-freemius.php(16352): Freemius->get_blog_install_map()
#2 /home/flooringsolution/public_html/wp-content/plugins/woo-checkout-regsiter-field-editor-premium/freemius/includes/class-fs-plugin-updater.php(85): Freemius->has_any_active_valid_license()
#3 /home/flooringsolution/public_html/wp-content/plugins/woo-checkout-regsiter-field-editor-premium/freemius/includes/class-fs-plugin-updater.php(70): FS_Plugin_Updater->filters()
#4 /home/flooringsolution/public_html/wp-content/plugins/woo-checkout-regsiter-field-editor-

Can you explain what the issue could be?

Many thanks!