Hello, as you see in the screenshot, the shipping isn’t available, and on the right side says to enter the shipping address despite being entered. No new app was added, and nothing changed previously related to such a thing, only regular customization without coding manipulation.
Are you using Shopify Shipping to help configure your shipping rates on checkout?
If so, the error message you’re seeing typically appears for stores that offer UPS shipping services. To ensure that shipping rates properly appear for international buyers, you’ll need to enable international services with UPS as listed in this guide. You can do this by following the steps below:
In your Shopify admin, navigate to Settings > Shipping and delivery.
Click on the relevant shipping profile (typically General shipping rates for most stores), and scroll down to your United Kingdom shipping zone.
From there, select the Carrier and app rates tab, then click on the ellipsis (…) > Edit rate.
You should then be presented with a list of the different services that UPS offers, and from there you can review the current services you’ve enabled to ensure that you’ve also included some international services for your UK customers.
Once you’ve enabled your desired international services, click Done > Save. You can then test your checkout once more to see if any shipping rates will now appear for UK addresses.