Tonight when I used LR5 to import photos shot in DNG and JPG from my Pentax K-x on a Mac running OS X 10.10 Yosemite, only the DNG files were previewed and included in my LR catalog counts. Eventually, I discovered the JPGs HAD been imported--they could be seen in the Mac's Pictures folder. But, as LR doesn't see them, I can't view or work with them in LR. I had no trouble importing both file types with LR 5 when I was using the earlier Mac OS Mavericks, but I've seen that other participants in Lightroom Forums who were using Mavericks and earlier Mac OSes have had problem importing JPEGs with LR5. Does anyone have a fix for this?
Have you checked your preferences in Lightroom. Something may have changed when you upgraded your Mac. e.g. Preferences> General tab> Import Options> is "Treat JPEG files next to raw files as separate photos" selected.
Thank you! That's exactly what was wrong.