I was previously able to see my clients comments on the Design Review page. The entire comment panel is now missing.
I've tried logging in and out of my account.
I've tried switching the mode from Design Review to Presentation and back again.
I've doubled clicked on a comment from the admin window listing of all comments. When I logged in to the Design Preview it showed the comment window pane but had an error message stating that comments were not available.
I've pasted the link directly into my browser, Chrome, Firefox, and Safari.
My clients and co-workers can see the comments and the comments panel just fine accross different browser types.
We are sorry to hear you're unable to see the comment panel in XD. We would like to confirm if you've tried using a different internet connection apart from the one you're using currently. Can you also try opening the link on a different machine?