Broken on WP 3.5.2 and PHP 7.4

I am getting a PHP Fatal Error when trying to use the SSO service.

PHP Fatal error: Uncaught Error: Call to undefined function login_header() in /home/[redacted]/webapps/[redacted]/wp-content/plugins/zendesk/zendesk-support.php:711\nStack trace:\n#0 /home/[redacted]/webapps/[redacted]/wp-content/plugins/zendesk/zendesk-support.php(86): Zendesk_Support->_do_remote_auth()\n#1 /home/[redacted]/webapps/[redacted]/wp-content/plugins/zendesk/zendesk-support.php(845) : runtime-created function(1): Zendesk_Support->__construct()\n#2 /home/[redacted]/webapps/[redacted]/wp-includes/class-wp-hook.php(288): __lambda_func()\n#3 /home/[redacted]/webapps/[redacted]/wp-includes/class-wp-hook.php(312): WP_Hook->apply_filters()\n#4 /home/[redacted]/webapps/[redacted]/wp-includes/plugin.php(478): WP_Hook->do_action()\n#5 /home/[redacted]/webapps/[redacted]/wp-settings.php(523): do_action()\n#6 /home/[redacted]/webapps/[redacted]/wp-config.php(113): require_once('/home/[redacted]...')\n#7 /home/[redacted]/webapps/[redacted]/wp-load.php(37): require_once('/home/[redacted]...')\n#8 /home/[redacted]/we...', referer: https://[redacted]/

I hope the application is still supported and the developer can look into this issue. I would hate to have to switch to another provider over this issue as Zendesk works amazingly otherwise.