Products that live inside another platform: how do you get people past the sign-up?

My app runs inside another company's app marketplace, so before anyone can try it they have to create an account on a platform they've probably never heard of. My first Reddit posts got about 380 views between them, and the install count didn't move.

For those of you building plugins, GPTs, Shopify apps, or anything else that lives inside someone else's platform: what helped people get past that first step? A short demo video, a sample they can see without an account, something else?