CS6 is not officially supported on MAC OS Sierra.
You can see if cleaning preferences and cache work for you: Troubleshooting 101: Replace, or "trash" your InDesign preferences
It is a matter of luck if it works correctly for you. I suggest that you either create a new partition having an InDesign CS6 compatible OS or upgrade to Creative Cloud [Edited].
Some useful links:
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Amaarora meant Creative Cloud, not Creative Suite.
Exactly. Thanks For Correcting me.
Thanks for your help, both of you!