My messages has been "updating" for quite some time. It gives the message please wait while it finishes or Quite Messages and relaunch which I do and it still goes back to the same message even afterwards.

Do you care about preserving the archive of old messages?

Back up all data before proceeding.

Triple-click anywhere in the line below on this page to select it:

~/Library/Messages

Right-click or control-click the line and select

Services ▹ Reveal in Finder (or just Reveal)

from the contextual menu.* A folder should open with an item named "Messages" selected. Quit the application if it's running. Move the selected item to the Desktop, leaving the window open. Relaunch the application and test. If there's no change, quit again and put the item you moved back where it was, overwriting the one that may have been created in its place. Otherwise, delete the item you moved.

*If you don't see the contextual menu item, copy the selected text to the Clipboard by pressing the key combination command-C. In the Finder, select

Go ▹ Go to Folder...

from the menu bar and paste into the box that opens by pressing command-V. You won't see what you pasted because a line break is included. Press return.