When the WordPress REST API cannot create or update a post, the mistake is often trying to debug everything at once.
It is easier to move in order.
- Is the site reachable at all?
- Does authentication work?
- Does the user have permission?
- Is this really a posts API issue, or a media API issue?
401 means authentication is the first suspect
Check the username, application password, and authorization header.
Testing /users/me first is often the cleanest way to isolate auth.
403 usually points to permissions or restrictions
The credentials may be valid, but the requested action may not be allowed.
User roles, security plugins, and server-side restrictions are common causes.
404 can mean the endpoint or setup is wrong
Check whether /wp-json/ is available and whether the REST API path is correct.
Also make sure post and media endpoints are not being mixed up.
If posts work but media fails
That usually means the problem is on the media API side, not the posts API side.
File upload handling, MIME types, and request formatting are common failure points.
