Hi, @thevaultapp !
Katy here from Shopify. I hope all is well with you, and welcome to our Community here.
The Hosted Payment SDK form is currently the only way to submit requests to integrate your own payment gateway solution. Could you let me know when you submitted this? If approved our team will reply to you within 30 days.
If it has gone beyond the 30 mark, I'm afraid that this would then indicate that your application has not been approved and that you would need to consider alternative options for your clients. If not however, although access is limited at this time, I would encourage you to keep an eye out until 30 days have passed.
I hope this helps!