...
To connect your Shopify feed to your cart, you’ll need to add a Product field. Please get in touch with support@preezie.com to help you with this
In https://doorman.preezie.com/home/importer/product-fields choose your Product database
Click Create New Field
Name: prz_shopify_variantid
Type: String
Field path in data feed: variants/id
Hit Submit
Now you have added a new product field you need to re-run your feed (or wait for it to run automatically) for each product to propogate the Shopify ID value into prz_shopify_variantid
To do it manually: Go to https://admin.preezie.com/app/products/feeds find your feed, hit Run
Once the feed has Success status, go to https://admin.preezie.com/app/products/products and find any product to check the new field is present, for example:
...