Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/c81e1ef42a9a29062a4ded9cb9fd0b94.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563