Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/151d053ff5a1c420a1a0cf4c2fee6de1.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563