iTunes won't open "because of a problem"!

Every time I try to open it, I get a window saying "iTunes cannot be opened because of a problem" and then says:

"Check with the developer to make sure iTunes works with this version of macOS. You may need to reinstall the application. Be sure to install any available updates for the application and macOS.

Click Report to see more detailed information and send a report to Apple"

Um, last time I looked, APPLE is the developer! I even spoke to a higher level Apple tech, and he was mystified, too. Great, so no one has any idea why this is happening or what to do? I'm thinking I may have to reinstall iTunes, and hope it won't mess with any of my files... but 25 years of using it, and only now it does this. I sure wish I never let go of iTunes 10, which always worked perfectly.