Memberships Not Working after PayPal Purchase

My memberships aren’t getting registered in the Directory Theme system after purchase through PayPal Standard Gateway. The order goes through in PayPal and sends user back to the site with Order Complete status but the membership level doesn’t get assigned. When I look at the user in the backend, it’s just —- no memebership —- under the membership and there’s no expiry date for it either. Any clues what’s going on here? Using v8.9 and having users purchase memberships prior to posting listings.