To start, this is basically a duplicate issue to the one in thread:
http://social.technet.microsoft.com/Forums/en-US/cb68ef93-cfc3-46d1-b033-fd911762fd93/application-catalog-displaying-no-applications?forum=configmanagerapps
However since that one is marked as solved I am unlikely to get anything out of continuing to post there.
To elaborate, I have the same issue as the above thread, the applications catalog was working for months after my SCCM installation but has suddenly stopped. There are plenty of applications published to the "All Users" collection and all site systems are green.
I have uninstalled/re-installed the applications catalog several times, I have even moved it to a completely new machine with no luck. Every time I move/reinstall it works perfectly but still offers no applications for installation.
Initially I was just going to let the issue sit as in the above thread the issue was solved without any interaction, unfortunately it has now been months and having to either manually install or use a device collection is beginning to become an issue.
I would start a Microsoft support case about this but we are currently in-between changing license types and as such getting support is a nightmare.
Any help would be greatly appreciated.