What it says in the title. When I click on the 'buy' option from item search on the site for a user shop, the button goes a lighter tone, indicating I clicked on it, but the sale doesn't process. It's the same for when I click on the shop name, search for the item, and try to click on it to buy it.
There's no errors with the Main Shops that are site-based. It's user shops only, for some reason.

I'm having the same problem. And you beat me to making a topic, haha :)