Does CiviCRM OG Sync support PHP 7 +?
We solved our issue - it appears to be related to a separate bug. The OG name we created had some formatting that either OG or the extension (or Civi) did not like

"Course Name 19-20: More things about the course: Subtext"

We changed it to "Course Name 19-20" and then it saved the groups, etc. and worked properly in PHP 7.1