LR6 suddenly won't export
I was using LR5 on a Mac desktop, and have been using it without trouble for years. Tonight, I went to try and export a photo (did not change anything), and instead of exporting, it brought up a Finder window, with "open" and "cancel" buttons at the bottom, like it wanted me to find photos? I tried restarting LR5, and that didn't work. Then I remembered that I had recently bought the LR6 upgrade, so I installed it. .....and the problem is still there. I have never seen this before! Any idea what might be causing it and/or what may have changed? (see screenshot below). I have not moved any photos, and they are all still in the same location on the HD.
I am running OX 10.11.6 (el capitan), 16GB of memory.
