You were definitely correct about the problem being in my footer, Andrew. Here is the troubling line and the error report in my local Xampp:

<?php echo nonameyet_copyright(); ?>

Fatal error: Uncaught Error: Call to undefined function nonameyet_copyright() in F:\xampp\htdocs\b2_nonameyet\wp-content\themes\20nny12\links-footer.php:4 Stack trace: #0 F:\xampp\htdocs\b2_nonameyet\wp-includes\template.php(690): require() #1 F:\xampp\htdocs\b2_nonameyet\wp-includes\template.php(647): load_template('F:\\xampp\\htdocs...', false) #2 F:\xampp\htdocs\b2_nonameyet\wp-includes\general-template.php(167): locate_template(Array, true, false) #3 F:\xampp\htdocs\b2_nonameyet\wp-content\themes\20nny12\footer.php(21): get_template_part('links', 'footer') #4 F:\xampp\htdocs\b2_nonameyet\wp-includes\template.php(688): require_once('F:\\xampp\\htdocs...') #5 F:\xampp\htdocs\b2_nonameyet\wp-includes\template.php(647): load_template('F:\\xampp\\htdocs...', true) #6 F:\xampp\htdocs\b2_nonameyet\wp-includes\general-template.php(84): locate_template(Array, true) #7 F:\xampp\htdocs\b2_nonameyet\wp-content\themes\twentytwelve\page.php(29): get_footer() #8 F:\xampp\htdocs\b2_nonameyet\wp-includes\template-loader.php(74): inclu in F:\xampp\htdocs\b2_nonameyet\wp-content\themes\20nny12\links-footer.php on line 4

That line is supposed to show a copyright date range something like 2012-2017, but I do not recall where I first got it and I do not know why it has suddenly become a problem.

edit: The [Visitor Maps] shortcode is still not working, but the Sidebar, widgets and Admin Bar are fine and maybe all will be well after I complete a file-by-file re-build of my Child Theme.