Troubleshooting

"Threadline is not configured."

Shown either on the settings page (as "Add your API URL and key…") or inside a block on the front end (as "Set your API URL and key…") — both mean the same thing: Settings → Threadline has an empty API URL or API key. The plugin checks both are filled in before attempting any request, so this specific message means it never even tried to reach Threadliner.

Fix: go to Settings → Threadline and fill in both fields.

"Threadline API URL is not set."

A narrower version of the same problem — only the URL is missing, but this specific message only surfaces from a lower-level check and is less common to see directly than the one above.

"Could not connect to Threadline: Threadline API returned HTTP <code>."

The plugin reached your API URL, but got back a non-2xx response with no usable error message in the body, so it falls back to reporting the raw status code. What it usually means:

Status	Likely cause
401	The API key is wrong, was revoked, or belongs to a different workspace
404	The API URL is missing a path segment, or points at the wrong host entirely
5xx	Threadliner's API is having an issue on its end — not something to fix in WordPress

Fix: double-check the API URL has no typos and no trailing path (it should be just the host, e.g. https://api.threadliner.io), and that the API key is current — create a fresh one under Settings → API Keys in Threadliner if in doubt.

"Could not connect to Threadline: <other message>"

If Threadliner's API returned a JSON error body, the plugin shows that message directly rather than just the status code — so anything appearing here that isn't one of the messages above is coming straight from the API response and should be self-explanatory (e.g. a validation error, if that were possible from this kind of request).

The connection test passes but a block still shows an error

The settings-page test only confirms the API URL and key work at all — a block-level error like "Could not load this form: …" means the specific form or list it's pointing at is the problem (most often: it was deleted in Threadliner since the block was set up). Re-open the block's settings panel and re-pick the form or list.

Still stuck

Check the site's PHP error log — wp_remote_request() failures (DNS resolution, connection timeout, TLS issues reaching your API URL) surface as WordPress WP_Error objects and get folded into the same "Could not connect to Threadline: …" message, so the log is the next place to look if the message itself isn't enough to go on.