With Squarespace, you'd generally link to the landing page rather than embed it. The embed option is only available via the Wordpress plugin. 

Hi Meggie! May I know the platform you're using for your products? The product needs to have a test purchase first before it appears on the drop down in the automation. :)

@rgb15 Are you using an inline form? I think it best to use JavaScript instead of HTML which is most of the time it works. Also, all changes in your Ck form on the Ck side will take effect immediately... (More)

Have you tried using the Squarespace code block when pasting the ConvertKit Javascript or HTML? This guide here may help: https://help.convertkit.com/en/articles/3864650-getting-started-squarespace-convertkit37