Hey Sylvain,
Sorry i misunderstood. In Backend Subscription page , those subscription will not shown here if user not clicked on checkout button, invoice still in no-status. Mean user only click on subscribe plan button but not confirmed the invoice checkout.
In PP4 , we decide not to show the subscription those are not confirmed by user , they just click on subscribe button but didn't complete the payment process. You can see those in backend User edit screen but not in subscription page.
In frontend we are showing these subscription , so if user want to do payment for that subscription then he can do it directly from dashboard also. This is the reason why these subscription not shown in backend subscription page.
Please check it again and correct me if i misunderstood.
Thank you for understanding !