We have a live rate feature for some customers, but an express rate requires the user to add a phone number.
However, if the user fills out the checkout form from top to bottom, the phone number is ignored.
The shipping rate does show up as if it was refreshed if the field is updated, but no request is made.
As a result, end-users do not get to see the express rate as it never is used in the shipping live rate retrieval request.
Is something cached on shopify, or perhaps the phone number is not taken into consideration to make the live rate request?
Also, it immediately updates once I change the address even slightly.
There’s a known issue with the phone number form field validation. It is being actively worked out right now and hopefully there will be a fix for that out soon. With these changes, it should correctly update the delivery options, and display those updates to the user, when a phone number is entered or updated.
Regarding caching, yes there’s extensive caching used at each layer. Given your observations, it presumably made the request when the phone number was entered, but not refreshed the display until a further update was registered. I believe the previously mentioned fixes to form field validation should resolve this.