Thanks for the reply John. The difficulty is happening on both my MacBook Pro and my Mac Pro. All the images I import to LR from the memory card are raw format (Nikon nef).
I have backup external hard drives attached to both computers. When I click Photo>Edit In>Adobe Photoshop CC 2015 the process goes to the external hard drive and opens that version of Photoshop.
If I eject and disconnect the backup hard drives and then try Photo>Edit In>Adobe Photoshop CC 2015 I get the dialog that asks whether I want to edit a copy with LR adjustments, but when I click yes Photoshop won't open. But then a mysterious TIFF shows up in my LR library.
If I try this by first opening Photoshop first and then Photo>Edit In>Adobe Photoshop CC 2015, the result is the same...nothing in Photoshop and the mysterious new image in the LR library.
The only way I seem to be able to get the image open in Photoshop is to drag the image thumbnail from the Library mode grid view to the Photoshop icon in the dock. Photoshop then opens and Adobe Camera Raw then opens the subject image. I then do my editing thing, click on the close X, and then click on save. I get a file browser window asking me where and in what format to save the image. PSD seems to be the default. I change it to TIFF and save the edited image file. It is NOT automatically imported back into LR. I have to click on Import, navigate to the new image file in the LR file browser, and then click Import again.
I'm running updated, current versions of OS X 10.11.6, Lightroom CC 2015, and Photoshop CC 2015.5.1.
Any thoughts?