Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/fb956d36e0754183f4f8c9d1f9550a30.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563