Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/3df6d2b3b202d27c1d3c23164a24563c.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563