Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/50d902321fc6e90f8456486e3b7f4c3c.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563