When I try to log into Flickr, I get a browser window opening with:

"Oops! Flickr doesn't recognise the API key this application is trying to use."

Also, and likely related, I get zero results with any search for images when trying to configure Flickr as a random image source for wallpaper.

I am running DisplayFusion Pro 7.3.2

I had the exact same problem. I'm happy to report the beta update fixed the issue