WordPress Error “Not a Valid JSON Response”
The “Updating Failed. The response is not a Valid JSON Response” error from within the WordPress Guttenberg Editor could be the result of a number of issues. If you do some googling, there’s lots of information and ideas on how to rectify the error.
PHP Composer and Wrong PHP Version
In the case I had, the issue was related to a custom WordPress theme using composer and requiring PHP 8.x but the site infact operating on PHP 7.4
Simple fix, change the PHP version to PHP 8.x on the sites hosting control panel.
Jordan Trask
With 20 years of experience in technology spanning Linux, Data Center Infrastructure, and related services and applications, Jordan consults with small, medium, and large organizations tackling technology problems and needs. With 10 years of experience in WordPress, he’s created Managing WP as a means of dumping his brain on the web.
Jordan operates LMT Solutions providing Technology Consulting Services and We Power WP for WordPress Care Plans and Support.