[Plugin: Ecwid: Random Products] thumbnails not appearing and code error

I’m only having success with this plugin about 50% of the time on my client’s gift basket site. Either the thumbs will not display or I’ll get this message:

Cannot generate shortcode for this configuration.
Cannot get product data.

Here’s the code I’m using:

[ecwid_random_products number="8" per_row="4" show_title="true" show_price="true"]

It is on the same page as the store widget code, but below.

https://www.ads-software.com/extend/plugins/ecwid-useful-tools/