How do I setup my store on a subdomain with multisite enabled?

After setting up everything on the super admin and multisite, I get a 404 page not found error.

Here is the site:
http://store.zekechan.com/

I created a product here:
http://store.zekechan.com/products/pre-sale-build-a-retro-game-with-zero-programming-in-24-hours/

When I hit the checkout button, another 404 page not found. Same with the products page. I'm stumped. Could someone kindly assist? Thanks.