Membership Premium plugin Payment Gateway return URL issue

I have taken this project over from another developer, so apologies in advance if I'm not completely across it.

I am having issues with the return URL after the payment has been made at the gateway. It gets stuck on the /paymentreturn/eway page rather than redirecting to the /welcome page. Furthermore, it is not adding a subscription to the member's account.

In the Payment Gateway settings, it says at the top of the page:

"In order for recurring payments to log properly you must enable your global instant notifications url pointing to /paymentreturn/eway"

However, I can't find any option in the eWay payment gateway's admin screens that allow you to set a notification URL.