Generate thumbnail and store locally not working on individual links

If I go into library settings and click “Generate Thumbnails and Store locally” it works for about 90% of the links.

Next I go to the problem link and click Generate Thumbnail and no change? I verified the link works and the page is valid?

The other problem is any link we had uploaded a custom logo/image for is over written.

Am I missing something obvious here?

https://www.ads-software.com/extend/plugins/link-library/