Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/989a7e2f450b008e502ac31f5c4c689e.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563