Acrobat DC and Acrobat Reader DC - Option to 'Send Comments' back to review initiator is missing?

Recently reinstalled software from scratch, including Acrobat Pro DC.

Received email-based review request from another writer -- when I opened the document, I did not get an option across the top of the pdf to 'Send Comments' back to the initiator. I know it was there in XI and earlier, not sure if it was in DC earlier. Thought maybe the other writer had simply saved as reader-extended with commenting on.

Now, when I sent an email-based review today to a SME who is running Acrobat Reader DC, he also did not have the Send Comments option. I verified with another SME that it still *does* appear in Reader XI.

I'm hoping it's just hidden somewhere in menus. Does anybody know if the option is in a menu somewhere, or if the functionality has been removed, or if this is a bug?

It's like pulling teeth sometimes to get people to do reviews, so adding in one more little roadblock (requiring them to save the pdf, then manually create an email and attach, then send) just adds to the frustration 🙂

Thanks!