I’ve got a error message like the one below on my client Website on WordPress and could not be updated.

Publishing failed. Error message: The response is not a valid JSON response

Looking at the error message, it seems that an error occurred when responding in a JSON file.

When I searched in my mother tongue Japanese, I couldn’t find many posts with the same problem, so I looked for a solution from WordPress users on the official WordPress website, and found that the problem was solved by installing the Classic Editor plugin.

As soon as I’ve got this information, I tested it and was able to update it.

Since I am used to editing with the block editor, it’s little hard for me to edit contents with the classic editor.

But I could solve the WordPress error and I don’t use very often the client’s website so I’ll keep using the classic editor for a while.

If you are getting the same error message on WordPress and would like a solution immediately, give it a try.