Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/106c2cf9a7b3a3ebe0f08b36ddd0c74c.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563