It seems, that covers can not be downloaded in many cases, in comparison to few days ago.
Tested with both (latest) versions of calibre. Seems, it is not the source of problem.
As the plugin was not uploaded, it is with high probability also not the source of issue, the source seems to be on Goodreads, they probably did some changes few days ago (I would say two days).
Please investigate, this is maximum from user-point of view. I am not programmer.
