Deleting the preferences appears to have helped.
However, still wondering how this jumped from my old MacBookPro to my new MacBookPro - I did not do a user migration - I started my new toy off with a clean install of everything and the problem persisted.
Jane-e - it did not matter how I highlighted the text or how much of it I selected - the field would not cooperate.
I am using the latest install available from Adobe CC - i.e. no updates are showing.
Steve appears to have helped with this one - have struggled with this since last fall - glad to see it may be behind me.