Google can't read XML sitemap

[dtwsolutions]

My client's VB forum is running the latest version, but we can not get the XML sitemap to be loaded in Google. It says "Sitemap index has errors" then has:

This required tag is missing. Please add it and resubmit.
Line: 3

The URL I have submitted to Google is:

/forum/core/xmlsitemap.php

The directory /forum/core/store_sitemap is 777 permissions and has three files in it:
vbulletin_sitemap_index.xml.gz
temp.tmp
index.html

I have VB set to automatically process the sitemap, but I also hit build sitemap manually but nothing changes. The .xml.gz file in this directory only contains:

<?xml version="1.0" encoding="UTF-8"?>
<sitemapindex xmlns="http://www.sitemaps.org/schemas/sitemap/0.9">
</sitemapindex>

If I open the sitemap URL that is submitted to Google, it just downloads a file, which shows the same 3 lines pasted just above.

I have Googled and Googled but can not find a solution to this. Please help!

[Wayne Luke]

Make sure the directory /core/store_sitemap is chmod 0777 and is recursive so the files are touched as well. Rebuild your sitemap in the AdminCP under XML Sitemap.

[dtwsolutions]

Thanks for the reply! That directory is already 777. When I click the button to build the sitemap, I see the timestamp update for the vbulletin_sitemap_index.xml.gz file that is in that directory. So I know it IS accessing it. Nothing gets added to it though. No content. And it's missing whatever parameters Google expects to see.

[Wayne Luke]

It isn't building anything in the file. Without a support contract and access to the server, I can't tell you why that is. Are there any errors in the PHP Error Log?

[David Uptmor]

Wayne, I am the one with the paid account for VBulletin. Customer number J3804E2EB891. Let us know what you need and how to get you the access details so you can assist. Thank you!

[Wayne Luke]

We would need a ticket through a support contract and access to the vBulletin installation on the server via the AdminCP and SFTP in order to diagnose what the problem is.