I ‘solved’ the problem by deleting all the contents of the blog-contents-plugins folder. I didn’t delete the folder. Doing that broke the site completely, as I laid out above. I then called Yahoo Small Business support and asked them to restore the contents of the folder. They were only able to restore the individual files and the wp-cache folder. They weren’t able to restore the plugins folders. That restored the site and made it so I can log in.
For YSB hosted sites, they recommend that you only install WP updates from their control panel, not the WP panel. For a non-tech person like me that is good advice.
Thank you,
