I have recently come across the following issue with Indesign CC 2017 on a Mac.
I am unable to click and select options in drop down boxes. When i click the box retracts but the original value remains. However i can hover over a selection with the mouse and press the space bar and it will select it.
No other computers are having this problem. I have tried uninstalling and reinstalling Indesign through the CC App manager to no avail.
If it happens on more than one file, try restoring your preferences:
If it only happens on one file, try saving as IDML and reopening:
Thanks for the quick response. The first option of trashing the application preferences appears to have fixed the issue!