I have an Early 2011 MacBook Pro (MBP) with iTunes not being accessible.
Is there a relationship between not being able to update further than 10.13.6 (High Sierra) and not being able to access iTunes? When I click the icon, I get a message (paraphrasing) "You can't open the application because it is updating." It's not. My MBP has 138 Gb of 318 Gb available. I vaguely recall getting a different error a few months ago (it could be many months) stating iTunes requires an update that may be linked to Capitan or Catalina?
MacBook Pro 13", macOS 10.13