Final Cut Pro X not updating

First off - (as of Oct. 20, 2019) what is the latest version of FCPX?   I have 10.4.6 installed.

I bought a plugin from Pixel Film Studios - I tired to install - their application warned me that FCPX isn't the latest update.   I open the Apple app store (purchased area) - nothing says an update is needed.  Then I just search for "Final Cut Pro X" (you know when you search to buy something) - I noticed right were it says FCPX it says "update".  Okay, I click the button.   It tells me it must close FCPX and FCPX will re-open once the update is done.   Well, it never updates.  Here's what happens FCPX closes then opens as expected - but the "update button remains gray and a little circle continues rotating forever.   FCPX remans stuck at 10.4.6.    So, what now?   Do I have the latest version of FCPX?  If not then how do I update?