XMLRPC Endpoint Blocked?
Resolving the Connection Refused Error in Ulysses Preventing You from Publishing to WordPress
The main error is about the XMLRPC connection being blocked by WordPress. To overcome that, you need to install a plugin that would act as a proxy to the requests. Sounds too complicated? Don’t worry.
https://ariel-lim.com/blog/ulysses-publish-to-wordpress/
(this resolved my problem – inMotion web hosting is great but blocks the xmlrpc … unless you rename it and use the Rename XMLRPC plugin)