PayPal checkout: Billing address – no where to enter

I am running a site for a nonprofit who mostly sell only virtual products – their memberships. I do NOT have the option to require billing addresses enabled.

When a user tries to purchase a membership, they get taken to PayPal correctly, but when they try to place the order, PayPal responds with a screen where name, email address and optional phone number are displayed. If a user then clicks on the order button, he gets this:

Billing First name is a required field.
Billing Last name is a required field.
Billing Country is a required field.
Billing Home address is a required field.
Billing Town / City is a required field.
Billing State is a required field.
Billing ZIP is a required field.
Billing details
Name: (Someone’s actual name as entered)
Email: (someone’s actual email as entered)
Phone (optional)
(someone’s actual phone number as entered)

I am unsure as to how to troubleshoot this problem. Is there somewhere else within WooCommerce that the billing info might be set to “required” ?

FWIW if someone tries to order an actual product such as a book, because the book requires shipping info, all is well and the order goes through.