I am working with a client who would like to get FedEx rates on his Shopify site, including FedEx OneRate shipments: A two day guaranteed service with special pricing when combined with one of four FedEx-provided packaging options. I see that any FedEx rating requires the Plus or Advanced plans, but does Shopify support displaying OneRate rates?
We will be implementing ShipStation for shipping, which supports OneRate, but we'd like to have rating options available on the site.
I would like to suggest you check out FedEx Rates, Labels and Tracking app. It supports FedEx OneRate by default and displays the rates on your cart/checkout page. You can even use it to print labels and offer order tracking.
But yeah, only if you're on the Plus or Advanced Shopify plans, you can use Shipstation for FedEx OneRate.
I am not sure Shopify supports One rate. FedEx One rates are displayed only if you send the right packaging to the API. For example, if you are using FedEx Small Box in the US or Canada, then the packaging type should be 'FEDEX_SMALL_BOX'. This is something which is missed by most solutions, hence the rates are not shown. However, as a note, if you are a shipper from any other country, then you have to send packaging type as 'FEDEX_BOX' to enable rates for One rate. All these can be easily handled using the Multi carrier app.