Bright is unable to process simple orders made via Guest Checkout.

This message is generated by the manageOrder callback in Bright, when there is no user ID associated with the order. In this case it must be a "simple"/non license key order.

Since the registration has to be associated with a user email address, and there is no user, Bright cannot create a course registration and therefore generates this error.

This is the reason the Bright is incompatible with guest checkout, for example.

You may be able to workaround this, if you are trying to manually create an order, by