Please,
I need your help to understand the reason after the payment with paypal the system doesn't forward any more to the url recorded in the field First Subscription Activation.

I tryed also to set the url for the Subscription Deactivation, but doesn't work either.

I need this to work since I have to set some custom fields based on a form that customers should select.

I need to open a page where the user have to select color and shape of a decoration kit.

The page is a php page already tested. If I use a joomla menu to open it, the page works correctcly and it shows a form where users can select from a radio button list. After confirmation, the decoration kit code is written on a custom field inside the user profile.

So, I was supposing to be redirected to that page after the paypal payment, but I was able to see it just once (perhaps an error?).

Now after the payments I see the normal payment confirmation: "Thank you for your payment of EUR 1,00 for the item purchased ..." but I can't reach my custom page.

The custom page is a normal Joomla article that include a "loadposition wrapper" since I need to get the JFactory::getUser() array. I set a new module with custom php code in the position wrapper. The php code makes the rest of settings. It checks tue user, a broser session, and a special password assigned to the kit, it updates some custom fields on database, and send a mail to other involved people.

I was supposing to run this custom page using the URL PLUGIN with the following url:
www.gerino.it/index.php?option=com_content&view=article&id=24&Itemid=157&user_id=[user_id]
As you see in the above url it's also important for me to be sure of the user_id, base on the field subtitution of CBsubs.

Do I understand wrong the attitude of URL PLUGIN?

And please, how can I solve the problem?

Thanks, I was starting to suspect something like your answer. In the while I made some modifications to my custom modules and I call it inside the Subscriber plan settings using "loadposition wrapper"
Paid Subscription -> Plans -> Presentation (tab) -> Thank-you text (payment completed):

I removed the URL plugin settings to avoid double routine and now my custom module is working: After the paypal payment, the user is redirected to the [Thank-you text (payment completed)] and the "loadposition wrapper" works perfectly, showing the form for the kit color and code selection.

But I don't want that a user could copy the url of this page: I tryed to copy the url of the paypal confirmation link, then, using another browser, I logged in with another user-account and then I pasted the url. In this way I got the same [Thank-you text] page within the wrapped module that allow the user to complete the same procedure without ever made the payment, because there is no user_id parameter in the url that comes back from paypal.

Since I set the subscriber plan to change the ACL for the subscriber user after the subscription payment, so I changed the ACL level for my custom module to the same level setted for the subscriber users, but I realized only now that the new ACL level for the users is active only after the logoff and login. So this solution is not usefull for my custom module.

In fact it happens that some of my menus are visible only for subscriber users, but just after the payment these kind of menus are not visible untill the user logs out and then logs in again.

Is there a way to apply the new ACL immediately after the paypal payment without the user has to logout and then login again?

This will help to protect my custom module from un-authorized users.