Nextgen gallery thumbnail error updating thumbnail
If you share any post on your Facebook page and it misses the thumbnail, then simply click on the Add Image (+) box to upload the image of your choice, and select it as the thumbnail of your post.
You may be confused about where to start in order to fix this problem, however there are few simple things you can do to make sure Facebook picks the correct thumbnail for your post. Sometimes this is the quickest and easiest solution, although it doesn’t work in all cases and it isn’t the most reliable.
Now, your post will tell Facebook which image you want to display for the thumbnail.
However, sometimes Facebook will continue to show the wrong image even after you’ve done this.
If you are using Yoast SEO, then simply scroll down on the post edit screen and click on the Social icon (it looks like three connected dots).
You can upload your Facebook post thumbnail here and it will show you a preview.
That’s because they have cached an old copy of your blog post. Facebook Debug tool is a simple and fast way to troubleshoot the open graph implementation on your Word Press site.