This problem has been reported before, but I have not been able to find a solution yet. Does anyone know why the Import dialog does not open when a memory card is inserted, and Lightroom is already open? The card is recognized, and clicking on Import shows the contents of the card and allows for the normal Import process to take place. But, the expected behavior is that inserting the card should open the Import dialog, and it does not do that.
Interestingly, inserting the card while Lightroom is not running causes Lightroom to launch (but the Import dialog does not open). I believe this is the expected behavior in this case.
Lightroom CC 2015.7
iMac (27-inch, Late 2012)
macOS Sierra 10.12.1
Memory: 24 GB
"Show import dialog when a memory card is detected" is checked in Preferences.
"Use Graphics Processor" is not checked in Preferences.
In the Operating System, Image Capture is set to launch Lightroom when the card is inserted.