Can someone explain to me why I'm getting a message that tells me to upgrade to Sonar Platinum when I launch Drum Replacer--from Sonar Platinum? Drum Replacer then does not do anything.  Nothing.  Nada.  Zip. 

Wait ... there's already an update for it--I'll try that.

What version does the Help > About screen show?

21.00.01 Build 254 x64.
Command Center is all green lights. 
The update did nothing.
 

The version of SONAR is too old to run the DR. The about screen indicates no updates have been applied to the core since the initial install. It requires 21.04 Build 27. The newest build 21.04 Build 30 should be installed if the SONAR Platinum line item was installed.

Okay--then why is Command Center not updating Platinum like it's supposed to? I've paid for a year, it's supposed to keep me current, right? It's not showing any updates.

IDK, in my case with every update the indicators in C3 show yellow for the line items which need updating and red for new items.
 
Are you claiming when running the C3 right now shows all indicators are green, like this:

 
Since the introduction of C3, did you ever manually install anything?
 

You know what ... it's me. I always assumed that the heading for Platinum (in Command Center) showed a yellow light because I chose not to download a couple of the items listed under that heading (such as local documentation, or a soundpak I know I'll never touch). It seemed to me that the heading might be yellow, if subheadings were not downloaded--so, I ignored it. It turns out that the heading is not merely a title, but contains update options itself.

I'm updating now.