Thank you for your reply…I was beginning to lose hope that anyone would!
So I did what you recommended but I found that the eye icon was open, not shut, and thought I had hit a dead end.
However, on further investigation I saw that the Protect Instances had the lock icon. So I searched the Instances to see a listing of courses that contained the Administration block and sure enough the troublesome course was not listed. So I unlocked Protect Instances, went back to the troublesome course and could then add the Administration block.
Thank you so very, very much!!
Now for my next question. Is there a good reason to have Protect Instances locked? My understanding is that only teachers and managers can see the course administration block. I think whoever did our upgrade and migration to a new server may have introduced the lock and I no longer have the opportunity to communicate with him as to his reasons or if it was accidental. If there is a good reason to keep this locked then I will do so and just temporarily unlock it whenever a new course is created so we can add the Administration block to it.