To customize and add surveys to your checkout experience, make sure your store is updated with Shopify's new checkout extensibility guidelines.
Identifying Extensibility Status
If you are unsure if your Shopify account has been upgraded to Extensibility, log into your Shopify store.
Then in the bottom left, go to the Settings menu, which will open up this screen. From here, select the Checkout settings in the menu on the left.
Then at the top of the page you should see a small box right under Checkout that describes your Extensibility Status. If you see an Orange box with the 'Upgrade to Checkout Extensibility' label and no checkmarks, that means you have NOT upgraded to Extensibility.
If you ONLY have upgraded the Checkout page, then you can continue to use the regular version of Compra. Extensibility will only affect your survey if you have upgraded the Thank you and Order status pages.
If you have upgraded both, then you will see a green box with the label 'Your upgrade to Checkout Extensibility is complete.' This will require you to follow the instructions contained in this document down below.
Note: Shopify's most recently deployed version of this may not have the Orange or Green banners to let you know of the status. In that case, you'll need to look for the 'Customize' box that will look like this screenshot (see extension instructions below for screenshots).