Thanks. That worked.
My usual routine after downloading and installing a JRiver update is to remove the old JRiver icon from my dock and then drag what I thought was the new icon from my Applications folder from my dock to the dock icons. But each time I tried that JRiver would still be 28.0.25. Reinstalling resulted in the error message about "update failed." Dragging the icon from my Applications folder in my dock to the dock icons resulted in 28.0.25 being the latest version again, even after installing from the link you provided.
I tried going to the Finder and opening the Applications folder, and then dragging the latest JRiver, 28.0.45, to my dock. That worked. I'll need to remember this new procedure. I will bookmark this post as a reminder.