Go to Shopify Admin > Settings > Shipping > General Profile > Manage Rates
Then scroll down to where your zones are listed.
Click '•••' next to the app, and click 'Edit Rate'
Make sure every service checkbox is checked.
Make sure Automatically show new shipping services to customers when they become available is checked
Why do I need to check all the services listed? What if I don't want a rate to show?
By a rule of thumb, you should have all services checked because, the app will still only show whatever rates have been configured within it.
Unchecking a service will make it so any rate from the app with that title will not show.
You should be managing all your rates within the app.
If you have troubleshooting issues, just check everything!