If rates aren't showing properly, go through this checklist
By ASR1 author13 articles
Make sure you have activated the 'Calculated Rate' feature on your shop.
Make sure all shipping services and 'Automatically show new shipping services to customer when they become available' is checked
Check to see if the app is in TEST mode. If so, use first name "Bambri" in the shipping address at checkout.
Try busting the shipping cache to pull in new rates you may have added since your last test checkout
Go to the Sync tab in the app, and 'Sync Shipping Zones' and 'Sync Fulfillment Services'
Check to see if any product in an order belongs to a product group that doesn't have any rates.
Make sure the product's location is part of the first location group in the General Profile
Make sure the products belong to the General Shipping Profile
Check to see if you have any duplicate rate titles, or rates with the same first 20 or so characters/letters in the the title.
Check to see if you have carrier rates that are actually available for the address you are testing with.
Verify that the app is added as a rate to your shipping zones
Read this if you aren't seeing USPS First Class Mail, USPS Retail Ground, or USPS First-Class Package International