Some graphic files grayed out in Place file selection dialog

I went to place a graphic in InDesign [15.0.2], several of the listed files were grayed out and could not be selected.  All of these files open fine in other apps, including Photoshop & Preview, and all have been used in other InDesign documents. 

If I drag the file to the document, it places it without a problem.

What could be causing this?