Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/4a1844b87f89c793f3241f5ca8a0b45e.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563