I’m also encountering the same issue. My library page has the titles of books, but images are not appearing and I get a warning in the plugin setup: Warning! You must provide your Amazon credentials and ensure they are valid. Requests cannot be made at this time.
This was working fine for years and has recently just stopped working. Let me know if I can provide any further information.
This certainly seems to be a bug. The $string on line 105 should be $str. This fixes everything.
