HTTP error: 500 Internal Server Error

500 Internal Server Error means that there's something wrong with your server or your script, maybe high server load, memory usage, script settings problem, script error, etc.

You should check your error_log, web server error log, syslog, script settings, etc, or contact your hosting provider or plugin's author/support and ask whether they can help :-)

If the problem is temporary only, you may just suppress the error by Ignore HTTP status code.