I see the thing I am missing is/was called Multi Login Restriction and it seems no longer supported. May I ask why? This seems like the sort of thing a subscription app would support by default.

Perhaps it is there and I dont see it. Or more likely, it seems just gone.

Perhaps if you used payplans to run a subscription site you'd see this from a customer perspective.

We are considering a move to wordpress and the crippling of payplans may make that move more imminent.

Please let me know if there is a Multi Login Restriction option in the 4.x version of payplans that stackideas created.

Hello Tom,

I am really sorry for the delay of this reply due to weekend.

We have deprecated the Multi Login Restriction app in PP4 because this functionality shouldn't be on payplans.
In PP4 , we rewample the worlkflow of payplans.

To achieve this functionality you can use third party plugins which will help you to restrict multiple login of user's on site.
Here is one useful plugin you can use to achieve this: https://extensions.joomla.org/extension/login-one/
You can check it out and use if it meets as per your requirement.

Let me know if you have any query.