Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/7a8c7bc5c013438fb9f7f852594e6cd6.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563