Hello, 

I've been trying to figure out why paypal and online invoice don't work for down payments. Searching throughout the forum and github but haven't brought me any answers so here I am. :)

The issue I fall into is when we sell an online service needing a 50% upfront down-payment, the automatic invoice which was created cannot accept online payments. Once a Sales Order is validated and down-payment is selected for either a % or fixed amount, it creates both invoices automatically. The first and primary invoice is unable to be paid through paypal or any payment acquirers and the "view invoice & pay" button disappears from the email template... (is_online is false ? )

 Not sure if this is a bug but here is my process. 

- Create a Sales Order with a product or service of choice    

- Confirm Sale and choose a down-payment % or set amount

- Create and View Invoices

- Invoice will be attached to SO with product named Down Payment qty 1

- Send by email and no "Accept and pay order confirmation online" appears.

Thanks for any help if possible and let me know if you can recreate this issue. Running latest March Odoo-10-c