Plugin crashes startpage

Hello!

First of all, I love this plugin, it’s the only CF7 to PDF converter plugin on the WordPress store that has all important features.

However, I installed the plugin on Friday and it worked like I expected it to. On Saturday I noticed that the design of the start page is broken but all other pages are still working fine. After enabling WP_DEBUG and WP_DEBUG_LOG I get the following logs in the debug.log file:

[05-Dec-2022 10:31:00 UTC] PHP Fatal error:  Uncaught Error: Class 'WPCF7_ContactForm' not found in /var/www/vhosts/pkb-performance.com/pkb-performance.com/httpdocs/wp-content/plugins/send-pdf-for-contact-form-7/classes/send-pdf.php:1902
Stack trace:
#0 /var/www/vhosts/pkb-performance.com/pkb-performance.com/httpdocs/wp-includes/class-wp-hook.php(307): cf7_sendpdf->wpcf7_add_footer('')
#1 /var/www/vhosts/pkb-performance.com/pkb-performance.com/httpdocs/wp-includes/class-wp-hook.php(331): WP_Hook->apply_filters(NULL, Array)
#2 /var/www/vhosts/pkb-performance.com/pkb-performance.com/httpdocs/wp-includes/plugin.php(474): WP_Hook->do_action(Array)
#3 /var/www/vhosts/pkb-performance.com/pkb-performance.com/httpdocs/wp-includes/general-template.php(3058): do_action('wp_footer')
#4 /var/www/vhosts/pkb-performance.com/pkb-performance.com/httpdocs/wp-content/themes/redparts/footer.php(41): wp_footer()
#5 /var/www/vhosts/pkb-performance.com/pkb-performance.com/httpdocs/wp-includes/template.php(770): require_once('/var/www/vhosts...')
#6 /var/www/vhosts/pkb-perfor in /var/www/vhosts/pkb-performance.com/pkb-performance.com/httpdocs/wp-content/plugins/send-pdf-for-contact-form-7/classes/send-pdf.php on line 1902

I already updated Contact Form 7 to the latest version and reinstalled this plugin. The only other plausible source of error could be that the WP Version this site is using is below 6.0 – but on the plugin page it says that it’s compatible with my version.

Any help is appreciated!
Thanks in advance!

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