Quote:

Try the default theme first as i mentioned before

No issues!
Try to troubleshoot by finding the problem.
As you see an only blank page, do the checklist one by one.
1. check the PHP version of your older server and newer one.
for that, create a new PHP file and write
phpinfo();
?>

execute the code on both servers and you will have a lot of info about both.

2. Check the config file and verify the database connection is established properly.
for that create a new PHP file and use simple database connection test code.
function OpenCon()
{
$dbhost = "localhost";
$dbuser = "root";
$dbpass = "1234";
$db = "example";
$conn = new mysqli($dbhost, $dbuser, $dbpass,$db) or die("Connect failed: %s\n". $conn -> error);

return $conn;
}

function CloseCon($conn)
{
$conn -> close();
}
?>

I hope this will help you.
PS: don't forget to use CloudFlare to prevent server level attacks on your website ( https://www.experthoot.com/protect-site-from-ddos/ )
Thanks

Tocai, you didn't transfer the Website properly, because when I go to:
https://www.melitonline.org
it redirects to https://www.melitonline.net

What you should do is to first make the https://www.melitonline.org working, and then redirect the https://www.melitonline.net to it.

You should follow the steps from this tutorial:
https://xoops.gitbook.io/xoops-2-5-9-install-upgrade/