Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/afbaa7b7d2d5c4f6816cc827d6e8abf6.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563