Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/a77f9a5a9c580ced24b77d0a08d04c25.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563