checkoutUrl from Storefront API 404 Not Found

[aseipel]

We are using Shopify in combination with a headless frontend. We were using the Storefront Checkouts API to redirect customers to the checkout but now switched to the Cart API in order to implement subscription products.

The integration was working perfectly for a few hours but suddenly the checkoutUrl in the cart response will redirect to a 404 page of the Shopify frontend.

We didn't change anything in the meantime, can anybody help?