Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/3b4c40d26d549b9a219a7e10f77dc328.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563