json error

An error has occurred: The response is not a valid JSON response.
Updating Failed. The Response is Not a Valid JSON Response

1. Check the WordPress URLs in Settings > General

WordPress Address (URL)
Site Address (URL)

2. Fix the WordPress Permalink Structure

Go to Settings » Permalinks

Save Changes

3. Regenerate the WordPress .htaccess File

4. Check WordPress Site Health tool.

Go Tools » Site Health

Take necessary actions.

5. Deactivate All WordPress Plugins

WordPress plugins may conflict with each other or the WordPress core software. Deactivate all WordPress plugins and then activate them one by one and check.

6. If all the above test fails, then temporarily Switch to the Classic Editor and check.

7. Further Troubleshoot switching to a Default WordPress Theme

8. Temporarily Turn Off Website Application Firewall

9. Turn On Debugging in WordPress

define( 'WP_DEBUG', true );
define( 'WP_DEBUG_LOG', true );