Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/4fa2f1b4823897f7ac89f4d8ea403065.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563