[Plugin: SI CAPTCHA Anti-Spam] 500 Internal Server Error

Hello
I have a problem

i install the plugin and the option “Comprueba si tu instalación PHP soportará el CAPTCHA” , “Check if your PHP installation will support the CAPTCHA” i click and open the url error: https://hazteescuchar.com/wp-content/plugins/si-captcha-for-wordpress/captcha/test/index.php

and the site dont show the CAPTCHA graphics, please help me. My site its https://www.hazteesuchar.com

Thanks, Alex