Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/8c8f1116897206de47fcb9b6e15fe18a.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563