When using the Nelio External Featured Image plugin, the grid will only show a blank box. The image shows on the post page, just not the grid>
Welcome to our forum,
Please note this plugin still has no support for external featured image, but great thanks for your post, it really interesting to me.
let me do something to bring new feature to use external featured image.
Please check 2.0.6 of Post Grid, i have added an option under “Grid Builder” > “Thumbnail” > External Featured Image(meta key)
you will need to put meta key for your external featured image, for your case its _nelioefi_url and then save the settings.
if you already set some featured image through Nelio External Featured Image plugin you will see external image will display on grid item thumbnails.
Please see the screenshot
If you have any issue please let me know.