bb17indo please check all log files for error messages, try in debug mode if that doesn't help https://docs.flarum.org/troubleshoot
In this case there is likely a javascript error as well, you will have to open your browser development tools and check what is printed to the javascript console tab.
If the website is on the internet and the error happens for guests, feel free to share a link where we can observe the problem.
As always, the php flarum info output would be useful. I'm not familiar with XAMPP but if you are running Flarum locally you should be able to access the command line and run the command in the Flarum directory.
