URL can't be reached? Can't fetch products and orders fail at checkout

Update: I’m hosting the site on a Droplet through NGINX btw

I’m trying to set up my store on my Jekyll site. The cart and everything is working but Snipcart can’t seem to actually connect to my website.

When I try to fetch products from the dashboard I get:
We encountered an error while processing the last request, do you want to try again ?

Order fails at checkout and gives me this error message:
URL of some products could not be reached. Review domain settings and product URLs. This entry on Order validation might help. See developer console for more details.

Developer Log:
We have not been able to reach the item at URL: . The URL must be available publicly. We suggest you take a look at the Security section of our documentation http://docs.snipcart.com/getting-started/security) to understand how the validation works. You can also take a look at this post that shows how to develop locally with Snipcart Develop a Snipcart Powered Website Locally Using ngrok).

and then:

Impossible to validate items for order . Please make sure the URL is valid, we suggest you take a look at our Security documentation http://docs.snipcart.com/getting-started/security) for more information.

Any ideas as to what might be causing this? I also get a warning that my test settings will “crush actual live settings” or something.

Can anyone help please?