So with he affiliate plugin it should update to approved automatically once the order is completed. We are seeing the PayPal Express orders as pending only for a short time while they checkout and then they automatically get marked as completed.
This is from the plugin creator:
When the order is initially processed we create a "pending" referral. As per the highlighted lines below in our WooCommerce integration, the referral is marked as complete when those last 2 actions run.
So when the order completes it should set the referral as approved, but for some reason any PayPal Express orders as being set as pending affiliate referral approval even thought he woocommerce order is marked as completed. Does that help?
What is your other suggestion and maybe I can try it.