After a fair amount of searching these posts, I was finally able to get this feature to show up. This seems like a bug a lot of folks are having. Hopefully, this will be fixed in the next iteration. I also have noticed a few things that if added could make this feature more functional:
Please add the ability to make changes directly (like pdf comments) from reviewers.
Some type of spell check would be appreciated especially since the panel is small and can't be expanded.
Why is there a limited character count on the designer's end? I find that I still have to send an email to the recipient for complex issues that need more explanation. Can this be removed?