The issue is not from Gutentor but sometimes while using Gutenberg the following issues may come.
Updating failed. Error message: The response is not a valid JSON response.
Publishing failed. Error message: The response is not a valid JSON response.
- Go to Settings => Permalinks. Select Post name and save.
- If it is already selected, you can just click Save Changes again.
- Make sure Rest API is working fine on your website.
- After that try to save your post/page again
Most of the time the Quick Solutions fix the issue.
- Make sure your installation meets the server requirement.
- Deactivate plugin one by one and try to save the post, if the plugin is causing this, you will find it.
- Delete revision post using any of the delete revision plugins.
Check if the issues is fixed.
- From your Cpanel file manager or FTP, goto WordPress installation and write following code on wp-config.php, see WP DEBUG
define( 'WP_DEBUG', true ); define( 'WP_DEBUG_LOG', true );
after that try to save the post and view the debug.log log file inside the /wp-content/ folder. There should be an error. Try to solve that.
- From your Cpanel file manager or FTP, goto WordPress installation and delete the .htaccess file. After that from WordPress Dahbboard to Settings => Permalinks. Select Post name and save.