When you say "open a web browser on the hosting server and click the link", do you mean that you're using File...Open in the browser to open a local file, or that you actually put the same URL (including hostname) into the browser regardless of which machine you're on?

If you're using local file access vs. web server access, that could explain some of the issue. It's possible that the Windows user running the web server does not have permissions to access the shares. If you're running command line, then you're running as some user, perhaps Administrator. That's not the same user that IIS (Apache?) is using

As others have noted, mounting the share as a drive will help some