SW EPDM 2015 preview window stopped previewing. Any thoughts?

If you start task manager is edrawingofficeautomator.exe or edrawings.exe running?

If they aren't the preview wont work.

Are you running 32 or 64 bit?

I don't remember the exact details but if you are running on a 32 bit system getting it to work properly is a complete pain. We had 2 people that had 32 bit pc's. We went and bought them 64 bit machines and the problem disappeared.

Depending on if it was a fresh install or an upgrade.

I had this same issue on a few machines.

In EPDM, right click Users, Under the Viewers settings, make sure the viewer for SolidWorks items is set to EDrawings 2015 EModelViewer.exe file.

The most common cause of this type of issue is Installing or upgrading Solidworks AFTER upgrading or installing EPDM.  Both install Edrawings, but in my experience, the Edrawings version which Solidworks installs breaks the integration in the EPDM preview window.  Simply running a repair on EPDM often works, but sometimes it's required to uninstall Edrawings first, then repair (which should re-install Edrawings).

There is also a method of fixing this type of issue which requires using regsvr to re-register the Edrawings DLLs but it's tricky and often doesn't work.  A re-install or repair is often faster and a more reliable fix.