Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/3f8af808bdb5b5bbb27600d4df84842d.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563