Mail Poet Error

Hello all,
unfortunately we also have a problem with MailPoet and get directly this error message:

MailPoet Fehler: Error: Call to a member function get() on null in /home/wp/disk/wordpress/wp-content/plugins/mailpoet-premium/mailpoet_initializer.php:40
Stack trace:
#0 /home/wp/disk/wordpress/wp-includes/class-wp-hook.php(310): mailpoet_premium_init()
#1 /home/wp/disk/wordpress/wp-includes/class-wp-hook.php(334): WP_Hook->apply_filters()
#2 /home/wp/disk/wordpress/wp-includes/plugin.php(517): WP_Hook->do_action()
#3 /home/wp/disk/wordpress/wp-settings.php(497): do_action()
#4 /home/wp/disk/wordpress/wp-config.php(60): require_once(‘/home/wp/disk/w…’)
#5 /home/wp/disk/wordpress/wp-load.php(50): require_once(‘/home/wp/disk/w…’)
#6 /home/wp/disk/wordpress/wp-admin/admin.php(34): require_once(‘/home/wp/disk/w…’)
#7 {main}

The typical solutions did not work:
Switching off and on again did not help.
Reinstalling the plugin did not help either.

What else can we do?

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