This has been an on and off issue for a while, even on Illustrator (mainly InDesign). I used to be able to click option and drag the image to duplicate it. However, it isn't working. It shows the little double arrow that shows it is duplicating, but when I drag the image, it doesn't duplicate it. The shift tool doesn't work either. It doesn't move my images in a straight line nor does it keep the proportions of images I am resizing. I have read so many forums and nothing works for me.
You almost certainly have a third-party piece of software which is grabbing your keystrokes. Lately, browser plug-ins (particularly Chrome apparently) have been the most common culprits, or security software which things disabling keystrokes is somehow useful.
Try restarting your computer and disabling startup software. Launch InDesign first and it will probably work fine.
If that doesn't work, create a new user area and launch InDesign to eliminate conflicts and corruption.