OK. Figured out the issue was a conflict with WordPress RSS Feed Retriever plugin. Not sure what to do as I need that plugin also.
I took a look and didn’t seem to have an issue with that plugin enabled. So, it could be something unique to your setup. If you basically get a white screen or some type of empty screen, then there’s likely a PHP execution error but you’d have to be in debug mode to view it. If you are not familiar with WP debug mode, there is info here: https://rocketgeek.com/basics/running-wp-in-debug-mode/ That might give you something to go on.
I saw there is a Security plugin to use with this. Is it required to have the full/pro version of the plugin to use that? I need the password expiration option.
There is a Security extension. It can be purchased individually or is included in the pro bundle. See this link for more info: https://rocketgeek.com/plugins/wp-members-security/