Hi @EthanFrasar! Is your catalog a public, hosted feed on an HTTPS URL?

Here are all the requirements for your catalog to sync properly:

• The catalog is a public, hosted feed of all the items in your catalog.
  • If you do not have your own feed hosting location, you can use a service such as Google Merchant feeds.
• The feed is in JSON or XML.  Check out an example feed in JSON and an example feed in XML.
• The feed is accessible on an HTTPS URL.
• The data in the feed is only one node deep, not nested JSON or XML (unless it is hosted on Google Merchant Feeds).
• The size of any one feed file should not exceed 100 MB; for optimal performance, we recommend each feed file not exceed 50 MB. If your file exceeds this amount, please split the feed into multiple files. All files used as sources will feed into the same catalog in Klaviyo.
• Required fields must not be left blank. For unavailable numeric fields, pass a zero (0), and for unavailable text fields, pass something indicating this such as “n/a” or “unavailable”.
• If your feed is hosted with a caching layer, disable caching for the location where the feed is hosted or refresh this cache when the feed is updated. Otherwise, Klaviyo will only pull updated data for the feed items after the cache is refreshed.

We have a super handy developer guide on this topic that goes into more detail!