Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/bb1bc9736480a379334e8997f0e4f7c0.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563