Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/e0b3dc5f3f8e6b7a7c9344d70b0defd2.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563