Payments not recurring in Paypal

Hello there.
We have been using the Yith free plugin with Woocommerce and have had a good few hundred sign ups for our memberships package. We are using the Paypal checkout with woocommerce. The payments all went through fine but we have since realised that these were not set up as subscriptions within paypal but just as single payments. So it doesnt look like any of these subsciprions will renew! What can we do?