Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/bf4ea0e7391800a14c4588565f0d561a.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563