The JSON error is usually a parsing error caused by unparseable content in the json result returned by the server after sending an ajax request, it is actually an error with the website itself rather than the plugin.
When the error occurs, you can use the browser’s developer tool(e.g., pressing F12 on Chrome) to check the specific error message, and then fix the error first. See the example screenshot below:
The loading error is caused by the JSON error. So, after you fixed the JSON error, the problem should be gone.