Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/c08d32cef7ad68c5f6b304673ac7f8a2.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563