Shopify returns the following error message preventing CartRover from sending the tracking information to Shopify:
This is caused by the Custom Order Fulfillment feature setup in Settings > Shipping within Shopify.
If you do not need this feature, please turn it off in Shopify.
If you are using this feature, you must tell CartRover which Custom Fulfillment service to pickup. If you do not, you could fulfill the wrong items and you will receive the error message when we post back tracking.
To set this up in CartRover go to the cart's settings page and enable: Filter Orders By Fulfillment Service
On the line below that, enter the name of the Fulfillment Service exactly as it is setup in Shopify.