If you have problems loading the list on the Tag Groups admin pages, this usually means that your site outputs a warning or alert that interferes with the data transfer to your browser. In most cases it is caused by another plugin.
If you see the JSON data, check any text before the opening curly brace. Example: Warning: xyz in /some-plugin/index.php{"data":"success" ... This text can help you identify plugins that cause notices, warnings or errors. Try if deactivating that plugin helps or consult your hosting provider if the error is caused by server settings.
If that doesn’t produce any helpful hint, try the following:
- Go to the Tag Groups settings menu and to Troubleshooting and System Information and check if the Ajax Test returns a green check mark. If not, you might find there more information where to search.
- Deactivate all other plugins and switch to a default theme. Then reload the Tag Groups Administration page. If now all seems OK, re-activate them one by one (and keep reloading the page) to identify the one where it breaks.
- Add to your wp-config.php file the following lines:
define( 'WP_DEBUG', true );
define( 'WP_DEBUG_LOG', true );
Then reload the Tag Groups Administration page and afterwards check the content of the debug.log file in the wp-content folder if there is any error message. - Open the JavaScript Console in your browser on the Tag Groups Administration page, reload the page and check the error or log messages for anything that gives a hint about the cause.