Currently when manual payments are made, the next due date in not updated on the product, this has to be done manually. If you do not do this, your recurring billing stops working as the next due date is always in the past.
This really needs fixing. It has caused us a lot of problems with customers not being billed and I suspect others have had this problem without realizing too.
I cannot think of any reason why I would NOT want to update the next due date, but at the very least it could prompt you when you apply the payment "do you want to update next due date" so that it doesn't get forgotten.
Featured Comment
If this is not occurring on your installation, you should open a ticket to discuss this with support.
WHMCS is unable to update the due date on a service when an invoice has been manually created as there is no link to the service(s) from that invoice.
If you require assistance with this, please open a ticket.