No worries, Marilyn.
Is there a good reason to have Protect Instances locked?
>> Yes, enabling protected mode on blocks will prevent users from deleting blocks. Hence, certain blocks like 'administration' and 'navigation' have protect mode enabled, as it could be quite difficult to retrieve these blocks if they are deleted.
However, I doubt if administration block was accidentally deleted on your Moodle site. And that's probably the reason, why you were unable to add administration block on any of the courses.
Could you try instructions below and see if setting 'administartion block to 'display site-wide' fixes the issue
- Go to Administration > Site administration > Plugins > Blocks > Manage blocks (or via the URL http://yourmoodlesite.org/admin/blocks.php) and unprotect the administration block by clicking the padlock icon
- Turn editing on in any course
- Go to the front page and use the 'Add a block' dropdown menu to add a administration block there, setting it to display throughout the entire site
- Go back to Administration > Site administration > Plugins > Blocks > Manage blocks and re-protect the navigation block.