Error whilst trying to install plugin

Hi

I’m trying to install the plugin however when I try and activate plugin, the following errors occure. Below is from my debug log.

[22-Sep-2021 00:11:45 UTC] PHP Fatal error:  Uncaught Error: Call to undefined function get_admin_email() in /home/markthem/public_html/wp-content/plugins/pdf-forms-for-contact-form-7/modules/pdf-ninja.php:147
Stack trace:
#0 /home/markthem/public_html/wp-content/plugins/pdf-forms-for-contact-form-7/modules/pdf-ninja.php(100): WPCF7_Pdf_Ninja->generate_key()
#1 /home/markthem/public_html/wp-content/plugins/pdf-forms-for-contact-form-7/modules/pdf-ninja.php(1090): WPCF7_Pdf_Ninja->get_key()
#2 /home/markthem/public_html/wp-content/plugins/pdf-forms-for-contact-form-7/pdf-forms-for-contact-form-7.php(335): WPCF7_Pdf_Ninja->admin_notices()
#3 /home/markthem/public_html/wp-includes/class-wp-hook.php(303): WPCF7_Pdf_Forms->admin_notices('')
#4 /home/markthem/public_html/wp-includes/class-wp-hook.php(327): WP_Hook->apply_filters(NULL, Array)
#5 /home/markthem/public_html/wp-includes/plugin.php(470): WP_Hook->do_action(Array)
#6 /home/markthem/public_html/wp-admin/admin-header.php(287): do_action('admin_notices')
#7 /home/markthem/public_html/wp-admin/plugins. in /home/markthem/public_html/wp-content/plugins/pdf-forms-for-contact-form-7/modules/pdf-ninja.php on line 147