Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/7e6f3afc686da62f253bf6b96d6c2a3c.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563