Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/9df8a6bc25e3813fc0b555a4582c09ea.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563