Your .webflow.io address and your custom domain were published at different times; publish both, then sync again.
The symptom. The CMS sync stops with a conflict, and new products do not reach Webflow.
Why. While the two addresses are published at different times, Webflow does not let the sync write items. It happens while you test changes on .webflow.io only.
The fix. Publish to both addresses, or go live, then run the sync again. Keep the stage where only .webflow.io is published short.