XML-RPC errors — rewrite error?

Also: Of note, this site was recently switched from Dreamhost, where I set it up 2 years ago, to VPS.net (not by me), so something may have been messed up in that process.)

You have WP in a subfolder, so logically the URL would be https://mermaidcottages.com/wp/xmlrpc.php (tested that on two sites, https://elftest.net/xmlrpc.php fails, https://elftest.net/blog/xmlrpc.php works)

It’s not finding ./wp-load.php which is … possibly an .htaccess conflict. What happens if you strip it down to just WP?

Moved the file into the subdirectory, not sure how it got moved up a level. All fixed now.