We are finding this problem right now, and I think I can contribute to this discussion. What happened in our case is:
An article is published in WordPress and a related topic is automatically created in Discourse.
However, for whatever reason (user post limit?), the new topic goes automatically to moderation.
The moderated topic is not public, The WP-Discourse plugin cannot “see it” and throws a first error message: Reason for failure: A bad response was returned from Discourse. Check that: - your Discourse forum is online.
If the moderator approves the post because everything is correct there, then…
When updating the article in WordPress in order to have a Discourse topic linked, the WP-Discourse plugin finds an article with an identical title / content, and this is what cause a second error message:
Reason for failure:
A 422 response code was returned from Discourse.
The solution is to delete the first Discourse topic and update the page again.
Yeah, I wonder why occasionally a post of these goes to moderation. It is sent by a trusted user. Maybe there is some kind of throttle? Several posts might be queued in WordPress, and then an administrator reviews them and might approve several of them pretty quickly.
Not in our case because we have the “Force publish” option enabled. Therefore the metabox only says.
The force-publish option has been enabled. All WordPress posts will be published to Discourse in the Kaosenlared category.
Once you know what is going on, it is not a big deal.
Could you try temporarily unchecking the ‘Use Full Post Content’ setting on WordPress and then updating the post again? If you don’t get any errors when you try that, then we’ll know that the problem is related to the content of the post. If you do get errors, then the problem will be related to the post’s metadata.