Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/2b5488ef2c41d94a34cc32d00a3c4561.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563