Dallman Ross

You’re welcome. I wish to add one more article to the collection of ones one might recommend on this issue:

https://blog.hubspot.com/website/json-response-error-wordpress

The reason I think this one deserves a look as well is that it includes a diagnostic tip that was important for me to understand the deep details of what was going wrong:

Check the [browser] console and debug log.

For more advanced users, you can try digging into your browser’s console or various debug logs to find a more specific problem. This isn’t really a solution for casual users, though, as you’ll need some technical knowledge to accomplish anything here.

There is a screenshot of the Chrome browser error console there, as well. For me, seeing the error messages on the browser console in real time helped me put two and two together and led to my finding the article I cited above on adjusting the apache2.conf AllowOverride directive to ‘all‘, which is what ultimately worked.

I’m coming back to this to post that finally I found a solution beyond the workaround the moderator showed me.

Try as I might, I still could not change Permalinks to anything non-default without the JSON publishing error returning. I meanwhile have read about a dozen interesting pages on this, one very good one of which was this one:

https://passionwp.com/response-is-not-a-valid-json-response-error/

But not even that solved the issue. Now, however, I found this gem:

https://codehunter.cc/a/wordpress/wordpress-jsonapi-wp-json-was-not-found-on-this-server

And that’s what has finally worked! Relevant text:

[E]nsuring that my apache2.conf file (located in the folder /etc/apache2) has its<Directory> directive ‘AllowOverride’ set to all rather than none

Yay!

Thanks very much, @t-p!

If that (i.e. Plain) works, then try reading Using_Permalinks before setting a custom permalink structure again.

Thanks, @t-p, that does shed light on a few things. ??

However, I am left scratching my head a bit nonetheless. The article says:

NOTE:
Your hosting provider should have set up the web servers with the necessary configurations for the Pretty and Almost Pretty Permalinks to work correctly. If they are not, then you need to contact your hosting provider.

Well, I’m my hosting provider. So, what’s the secret trick to setting up my configuration for a Pretty Permalink structure I prefer?

It was rather a trap for the unwary that caused me to spend many frustrating hours trying to figure out why I couldn’t post after the sticky-wicket thing I had done was to select a different option on a quite accessible and inviting configuration screen, after all…

I’m near to ready to mark the thread as resolved, but I’d still like to know what those “necessary configurations” might be.

Okay, sorry. I thought the very same symptoms were proper to post in the same thread. I would delete it now if I could, but I don’t see a way to do so. I solved my problem. (I used command-line tools on the server.)

Good luck to the O.P.!

Well, I have the same problem after I put wrong site data in the WP control panel, and now I can’t get to it anymore and port 80 throws an error. I am my web host! It’s my cloud server. I set it up. I have Linux server shell access under Ubuntu 20.04. But I need to know where the config files are on the server and how to undo my error.