This is not done by administration, this is something you should do yourself. (But yes, I faced some bugs in the past, so it could be some bug, but you still can fix it).
Edit the article and pay attention for the right area where the downloads are managed. Make sure you actually download the file, not just select them. Use correct file URL when you have it downloaded.
You have to add the link yourself if you are missing it. Here is the format for the source code link:
<ul class="download">
<li><a href="yourCode.zip">Download source code — 666 KB</a> </li>
</ul>
—SA