You could try to revert to MacOs 10.15.3 - 10.15.3 is still available.

Did you try reinstalling them?

You’ll likely have to do a Time Machine Restore if you can’t reload the plugins.

Good news!  I reinstalled them, and I got them to work after a bit of tweaking.  This is kind of complicated, and for those of you who upgrade to 10.15.4, here is how to deal with this!

Once you open Finale you will start getting these messages saying that jw. . ..bundle cannot be opened, etc.  There will be options to move to trash and cancel - AND a question-mark on the left.  Hit the question-mark, and another dialogue will open giving you a link to open settings, security and privacy.  Click that (or forego the question-mark deal and just go to "general" in settings, privacy security).

Hit cancel

THEN go to security, and the first jw plugin on the list will be mentioned. Click "Allow Anyway".  As soon as you do that, the process will begin for your next JW Plugin.  This process needs to be repeated until you have allowed all your JW Plugins!!

Next, close your document and open it again.  This time you will get a dialogue that gives you the option to open each plugin.  Click "Open" for each plugin.  The next time you open Finale you will NOT have to go through this.

Evidently this is a new safety feature in Mac. . .

Thanks!

John

Good. I was hoping that's what it was.

This has been around in varying degrees since Sierra and tightened up in each subsequent OS release. A couple of my apps did the exact same thing with already installed apps and plugs when I upgraded my test machine to 10.15.3. Don't know why yours waited till 10.15.4.

Chances are good you'll see this again from something.

If an installed app gives you this grief, right-click and select Open. You shouldn't have to do that again.

Thank you for the solution!!  

JOHN MOODY, you are a life saver!  Thank you for birddogging this and then detailing the steps to fix the issue.

I just upgraded to Big Sur. Thank you for posting this solution!!