I use ManageWP. It updated about 15 blogs tonight and I got email alerts that they all went offline. I rolled the Akismet plugin back to 5.3.3 and they’re back up. When I try to manually update in a given site’s dashboard it says it can’t. I tried deleting 5.3.3 and just installing the latest version from scratch and it just said “fatal error” and didn’t install.
Server requirements listed on the page for WP version and PHP version are both met, so I’m starting off from the assumption that it’s not those. I use server logs instead of WP logs, and my server just keeps saying something about a possible syntax error on line 159 of class.akismet-admin.php, but when I look over the whole file nothing stands out to me. Figured I’d pass it along.