OK, I have been able to duplicate the "blank message" when I click on a newly replied to message.

I did this by going into the computer forum and setting the "Expand topics" setting to Expand Topics. (Collapse topics will be displayed it the topic is expanded.)

To again view new replies I Clicked On Collapse so that it disappears and is replaced by Expand and then closed and re-opened my browser.

I also see that in Expanded mode while in the computer forum (where Expand/Collapse is selected), clicking on an original post displays the message and all replies but clicking on any of the reply messages displays a blank page.

Maybe this or something similar is causing your issue.

Jim.