Mac or Windows?
Are you using a card reader or directly connecting the camera to the computer? (Card reader recommended.)
What happens when you do the import from the Df?
Do the files get copied?
Do the images show up in the Library grid?
Thanks for your questions Joe. I'm working in an OSX environment and it seems the update I did solved at least part of the problem.
I'm working with an iMac that has an SD card reader built is. I use that to download images. Lightroom responds when a card is inserted in that slot and indicates where the images will be copied per my instructions. This is all familiar to me from years of using LR with my D700. (I use a firewire card reader when downloading from the CF card used in that camera.) The images would appear in the Library after download and I could work on them, but when re-opening LR for another session the photos and the album I copied them to did not appear in Lightroom. I can find them on the external drive I'd selected but LR didn't list them, at least until today after the update. It may be that 5.7 didn't recognize the Df but 5.7.1 does. The Df was released only about a year ago. The question now will be whether files from BOTH the Df and D700 will be mingled in one folder or not. The first time I shot the Df I also shot with the D700. The D700 images were in the folder which I title by date shot but the Df images did not appear. It was all very bizarre. But I believe my problem was solved with the update. All the Df images I've taken in the last nine days are shown in the correct albums. I appreciate you're contacting me however. Thanks.