Subject: Custom shipping 'add rate' related issue.
Step 1: We have created the app it is installed. http://prntscr.com/ojpgib We have posted this API.
Step 2: We can see this 'carrier service' in the Shopify store (https://prnt.sc/ojprlu).
Step 3: We tried keeping the static response of the rate (https://prnt.sc/ojpr2z).
Step 4: If the shipping is done we could see this error message in the frontend http://prntscr.com/ojppvd
Step 5: In the call back URL we have to pass the data https://prnt.sc/ojph3j so how can I pass this data?
*If we can do it with static response, can you please guide me to do know the process.
Please let me know if you can help me it would be really helpful.
The error you see in step 4 occurs when the cart that was used to create a checkout from has changed and the selected shipping rate is no longer valid. This validation happens when selecting a rate, clicking continue, and the validation that takes place under the hood determines the rate is no longer valid.
As for how you pass the callback data, you would simply respond to the POST request to your callback url with a JSON object called "rates". The object would look like how you have it in step 3.
Let me know if you continue to have trouble.