So in order to use our app or any 3rd party shipping app, you need to have the Calculated Rate feature activated on your shop, even if you are not actually using real-time carrier rates within our app.
The calculated rate feature is required to allow our app to connect to your shipping zones, and have permissions to show rates at checkout. This means that even in order to use the app in Test Mode, the feature is required. This feature is necessary to have to demo/test any 3rd party shipping rate app, not just ours.
Add it for Free to any Shopify Plan
You can activate this feature for FREE on any Shopify plan by switching your Shopify billing to annual/yearly.
Then you contact Shopify support ( via Live Chat or by Phone ) and explicitly make a request for the calculated rate feature to be added, and will add for free.
Tell them:
I've switched my account to annual billing, can you please add the Calculated Rate feature to my shop for free
Add it ala carte for $20/month
Alternatively, you can add it ala carte for an extra $20/month, also by contacting Shopify support and making an explicit request. This $20/month fee will be in addition to the subscription charge for the app.
Tell them:
I'd like to add the Calculated Rate feature to my shop for $20/month, please.

Next in Getting Started

Getting Started with Advanced Shipping Rules
Before you Start
Calculated Rate feature is required to be active on your shop
How the app connects to and syncs with your Shopify Shipping Settings
Configuring Rates
Testing Rates and Going Live