Customer must login to complete payment. Why?

Since the release of version 2.7, Easy Digital Downloads has included the ability to recovery abandoned or pending purchase records. If the user's browser is still in its purchase session, the product will remain in the cart for the user. Likewise, a Recovery URL section is added to the admin purchase record, allowing site admins to easily share the link with a user in the event his or her purchase session has expired.

If the user has never purchased before, the process is smooth. Using either the recovery URL, or continuing the purchase session, the user can continue on with the purchase as if nothing ever happened.

However, if this user, identified by the email address entered at checkout, has made a purchase before, that abandoned or pending purchase record is now attached the that user's customer record and can only be recovered by him or her.

In the event that a logged out user attempts to recover a purchase that is tied to an existing customer record, a notice similar to this will display on checkout:

This notice means that the purchase record used to populate the checkout cart is directly tied to an existing customer record, meaning the email address entered by the person attempting to check out matches an email address from at least one past purchase.

Let's go over a few quick solutions to overcome this notice based on scenario.

I'm the site owner and I'm facing this notice while testing

If you are the site owner and you have logged out of your site in order to test the purchase process for a guest, there is a chance that you have used the same email address for testing that you already have attached to your live account. That means, in your testing, you are trying to recover a purchase record (as a guest) that is now officially attached to your live account. That will cause you to see the notice.

You can even log into your site from another browser, view the abandoned/pending purchase record from admin, and see that it is already attached to your customer record. In this scenario, the notice is accurate. If you would like to test the guest purchase process, please do so using an email address that is not already attached to a customer record in your store.

One of my customers has reported this notice to me

This scenario is the same as above, except it may be more of an edge case. Chances are, you allow guest checkouts on your site, which is fine. However, even when someone checks out as a guest, a customer record is still created based on the email address used at checkout.

In theory, a customer can make 10 separate guest purchases over the course of a year, using the same email address each time, and each purchase will still be attached to a single customer record. 

This is desirable, and good for your system. However, if that repeat customer attempts to make an 11th purchase, abandons the purchase for whatever reason, and then attempts to recover it either through browser session, or because you provided a recovery URL, he or she will have to login to complete the purchase. This proves to the system that the rightful owner of that particular purchase record is completing the purchase.

This scenario is rare, but it can happen.

Note: we have concrete plans to make the recovery process a little smoother so that store owners can run a store that fully supports guest checkout in all scenarios. If you still see this note, the change has not been made yet.