Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/b5ef0217da68b6d6a95f7fc51482e1d5.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563