An endpoint returns 404

A 404 from a Memberside route means the route is not registered. Three things cause that, in order of likelihood.

The endpoint group is off

Every endpoint ships disabled, and a disabled endpoint returns 404 exactly as though it did not exist.

Go to Memberside → REST API and switch on the group. Changes apply immediately — no cache to clear, no rebuild.

Find the group for your feature in the endpoint matrix.

Permalinks are set to Plain

The WordPress REST API needs pretty permalinks. With Plain, every route 404s, including WordPress’s own.

Go to Settings → Permalinks and choose any other option. You do not have to change anything else on that screen; saving it re-registers the rules.

The tell is that everything fails at once rather than one feature.

The plugin providing it is not active

Groups whose backing plugin is absent are not registered at all, so their routes 404 even when the group appears to be enabled — the group will not be listed.

If a group you expect is missing from Memberside → REST API entirely, its plugin is not active. See A feature is greyed out.

The route exists but returns an empty list

Not a 404, and a different problem. The endpoint is on and answering with nothing, which usually means the individual item has not opted in:

Forms — each form needs Show this form to REST API.
Member directories — same switch, on the directory.

See Forms and directories.

The namespace changed in 2.0.0

If you are testing routes by hand, or following older documentation, note that the plugin moved from um/v1 to memberside/v1 in version 2.0.0, with no alias. The wall endpoints are memberside/v2.

Requests to um/v1 will 404 on any current install, and any guide describing those routes is out of date.

Narrowing it down

What fails	Where to look
One feature	That feature’s endpoint group
Every Memberside feature	The Site group, or the connection
Every route, including WordPress core	Permalinks
A group is missing from the admin list	Its plugin is not active