The issue is not related to Webflow if the assets on Webflow are loading normally. You would probably notice the same behavior if you viewed the ecwid shop from your browser directly. Most likely it is a local issue for you. You can always check the status of Ecwid to see if they are having an issue.
I believe their component is just slow loading unfortunately. I also tried troubleshooting this about a year ago when I created my shop, but unfortunately is just on Ecwid’s side. I had the same experience with the Shopify Buy Now button component.