Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/78aa3b1b8a884851e3c11c756c2390e2.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563