Hello @MarianT,

Sounds like the feed file you are attempting to upload is too large! In order to sync a custom product feed to Klaviyo, you’ll want to ensure your feed aligns with the requirements mentioned in the the Sync a Custom Catalog Feed to Klaviyo document. One of these points highlights how your custom feed file should not exceed a maximum of 100 MB. 

• 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 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.

I would also suggest making sure you are importing your custom product feed within the Catalog tab and not the Data Feed tab. The Data Feed tab is used for importing and connect web feeds which would be different than a product feed. Web Feeds also have a much smaller limit where these sort of files must not exceed 3.9 MB in size as detailed in the Guide to Adding a Custom Web Feed in an Email Help Center article. 

I hope this helps!

David