Hey Tim,
Please let me clarify first that, yes, it’s generally best to test in staging. But, API requests sometimes are restricted only to one domain and that is usually the live domain. That is why I asked to test the live site but keep a backup so you can revert to the working state. Thank you for confirming that the issue persists. That also answers Rad’s question. I’m also sorry if I missed that you already have tested previously. I got lost in the back and forth conversation here.
Now to the video thumbnail issue, I checked the URL you posted and the thumbnails weren’t loaded and the CORS issue wasn’t resolved as you can see in the screenshot below.

Aside from CORS, the play button you see missing is due to Hummingbird.
I’ve deactivated all third-party plugins in your test site and made a test page at http://www.staging1.elasticlounge.com/apex-support-test?avoid-minify=true and I see this.

There’s no video thumbnail but there are no more errors in the console.
Now that it’s clear, Ilve investigated further and I first tried setting the Vimeo thumbnail in your grid. Previously, you’ve set it to Featured Image. But, this didn’t resolve the issue.

It looks now that something has changed in the Essential Grid. The z-index of the poster image is now 0. Setting it to 1 resolves the issue. I’m still looking for the setting for this but for now, I’ve placed this CSS in Theme Options > CSS to override the display.
.esg-grid .esg-media-poster {
z-index: 1 !important;
}
Video thumbnails now display. Please apply the CSS to your live site.


Hope that helps.