Loupe tool not working in Adobe Acrobat Pro

Is there a fix for the Loupe tool in Acrobat Pro?

You upgrade to the new Adobe Pro and the Loupe tool works for a few days and then stops.  All you then get is the blue outline box but no preview window.

Myself and my colleagues have had the same problem with the tool through 3 upgrades at least (we're now on PRO DC).  The only solution I've found in the forums is to reset the Preferences but from the responses it's doubtful that solves the problem .  Thankfully, I can't locate the preferences file on C:\ they reference (brand new PC by the way) because for the effort involved I might as well reinstall Pro DC again.. 

The problem has persisted through several updates of Adobe Pro.  Surely Adobe has a fix?