s2Member includes the payment gateway integration. In the s2Member Framework is just PayPal Standard, but s2Member Pro adds Stripe and a few more.
I see from what you said earlier that you use Stripe. s2Member Pro already includes it. If you can't find it in the navigation, make sure you activate it first from WP Admin > s2Member Pro > Other Gateways
You're using the Stripe Pro-Form in that page, so you can see it in the navigation, so the gateway is enabled in your s2Member Pro already. Then you can configure the integration with it from WP Admin > s2Member Pro > Stripe Options
Why do you feel you need another plugin for s2 to work with Stripe? Are you doing it to get some extra feature? I'm trying to understand better what you have set up.
I look forward to your update.