OS 10.11.6, 2010 iMac but that doesn't matter because the issue is store.makemusic.com and the Chrome browser.
Unlike many, I did not get an email to update my Finale license for $125. Instead, I got an email to update my site license—I don't have a site license but I do have more than one valid license for Finale. I don't always upgrade them all.
OK, I bought a Finale 25 upgrade through a reseller, paid the money and was emailed a download link and upgrade code. Ok...
I went through the motions after logging into my account and seeing that each of my licenses were eligible for upgrade.
I punched my upgrade code and 2011 serial number. It asked to verify that I wanted to update that 2011 license to Finale 25. I click yes and get an error that my 2011 license isn't eligible for upgrade. What? Yes it is.
OK, I try a 2014.5 serial number, go through the same motions, verify that I want to update my 2014.5 serial number to Finale 25 (I don't really but...) and it validates my upgrade ... to Finale 2014.5!
As I was writing this up, it occurred to me to try the same thing (updating my 2011 ser#) in Firefox and that worked. Since my account is now properly updated, I will not be able to try this in Safari.
If I save someone the frustration that I went through, I'm good.