First, how did you "upgrade" from Office 2011 to Office 2016? Myself, I uninstalled most "pieces" associated with Office 2011, and then did a clean installation of Office 2016.
Secondly, do you have the latest version of Office 2016, V15.35? If not, you can get the individual modules from here:
Third, I do not use Powerpoint, but here are the results of a google search for "Issues with opening up saved Powerpoint documents created with Office 2011 for the Mac with Office 2016 for the Mac":
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