Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/a9161be3c5e6c2ba83c7c715b097e31c.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563