Once in a while you do something that seems simple but creates lots of complications.
So I decided to edit the theme name and renamed the theme directories locally and on the server. Then the site vanished, so I promptly changed the names of the directories back. The site was still gone, plus the theme was no longer showing up in Presentation > Themes.
I can get to the css file.
But if I try to go to other theme files (e.g. the footer) I get error messages like Fatal error: Call to undefined function: wp_footer() in /htdocs/test/wp-content/themes/wp-andreas01-12/footer.php on line 5.
I've deleted the contents of the cache.
I've re-uploaded everything in the theme directory and the wp-admin directory.
Any ideas for getting the site up and running again?