Missing Thumbnails

Hi @jedan.

Thank you for reaching out.
I double checked the issue and can not reproduce it. Recent Posts Widget With Thumbnails works also with WordPress 6.1.1.

I double cheched your website and found out, your have added the following style:

#rpwwt-recent-posts-widget-with-thumbnails-2 img {
  width: 0;
  height: 0;
}

It sets the width and height of the thumbnail to 0. So, the thumbnail is available but with a sitz of 0. Thats why you do not see it.
I saw you are using a minifier. Maybe it helps if you flush the cache?
Nevertheless you have to remove this style to get the visibility of the thumbnails back.

Please let me now if you need further help.