I have looked into the response that my server replies with - and everything seems ok - the app was also working previously - and I have looked into similar topics here on this forum only to found that most were missing an intermediary response or some kind of other issue.
Now I'm wondering if the issue might be a timeout - as sometimes the reply takes 2 seconds to be given
I also have some doubts on the content of the reply itself - as in the docs it does not state what kind of JSON it is e.g. JSON allows unquoted numbers and booleans (and there's both a number and boolean there)
Regardless here's the initial support ticket I wrote to Shopify support - only to find out after 4/5 emails that they don't give that kind of support anymore via email.. *sigh*
yes @URLify-me - it has been a long time - but it was either lacking the CarrierService to be registered - and/or the shipping method configuration to specify the usage of the carrier service
so - basically just double check all of those and the format - and but a debug point - make sure you get the request from shopify - if you give a reply - make sure it's in the right format - etc
What do you mean with "shipping method configuration to specify the usage of the carrier service"?
The following? I am only selling to France. I don't know whether I miss any configurations, as I see my API Carrier Service under "Carrier and app rates"