Installing version 20 does not remove version 19 and so the likeliest explanation for your problem is that you're still using the shortcut for version 19. In the Start menu you will find a shortcut for version 20, so use that one instead.
Thx! I checked in control panel. There is only version 19 record, no 20 record. When I play my music, the screen is still JRiver Music Center 19. I expected it was not properly upgraded. BTW, I am using Win 8.1. Is it the problem?