Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/72a56a0ac3277998646d276e0d6e4ea1.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563