You may have noticed your Autodesk Application Manager that was installed with your 2015 Autodesk products has stalled when it looks for updates. You'll see only the continuous search indicator that will run as long as you allow it, that looks like this:
According to Autodesk's KB article this is due to your local antivirus real-time scanner blocking access to the Autodesk updates server on the web.
For the Application Manager, open your antivirus scanner's control settings and add the executable for "AdAppMgr.exe" to the exclusions list.
AdAppMgr.exe is located here:
For example, for Windows Defender and Microsoft Security Essentials, that looks like this:
Once this exclusion is saved, then start up the Application Manager and you should see the correct update status. Note: You can also double-click the AdAppMgr.exe from the path shown above to load the Application Manager after setting the exclusion.