How to accept PayPal payments

Hello! I’ve looked everywhere and can’t find what I need. I’m trying to emulate the same functionality as my last invoicing software which is no longer being developed.

I want to send a pdf invoice through email. In the email, have a link that goes to their portal where they can view the invoice and click ‘Pay Now’. I have the PayPal Express setup with the correct API username/password/signature. But when I follow this journey in the portal, and click ‘Pay Now’ a small shadow box comes up with no options:

Any ideas?

Ok, seems like it is working now… we’ll see…