Symptom: On WordPress sites hosted at Rocket.net, the Solid Security (formerly iThemes Security, now Kadence Security) setup wizard fails with errors like "Could not save user groups: No route was found matching the URL and request method", and saving any Solid Security settings page fails with "No route was found matching the URL and request method." Settings never stick. Rolling back the plugin and importing a settings export don't help.
Cause: This is not a plugin bug. Rocket.net's edge (CDN layer) mangles any POST to WordPress core's REST batch endpoint (/wp-json/batch/v1) that carries a non-empty requests array: the request's method is changed and its body is stripped before it reaches WordPress, so WordPress answers 404 rest_no_route. Solid Security saves its wizard results and settings-page changes through that batch endpoint, so every save fails. The same request executed server-side (bypassing t