Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/9c93a0d2b29c09353666cf34e837b8e3.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563