Disappearing legend items when exporting to PDF.

[AllisonBoblit]

I would like to export my map to PDF, but when I do that the colored boxes inside the legend disappear. Here is what I am seeing in ArcMap:

But when I export to PDF, it looks like this:

The Tract layer is ArcGIS Map Service's online content, 2015 USA Median Household Income. I tried exporting to JPEG, same story! What should I try next?

[DanPatterson_Retired]

what version of arcmap?  issues have been reported before, but some/all seem to have been resolved through the various version updates in arcmap