I've just begun to have this problem when a book is included in Kindle Unlimited:
Spoiler:
Get
https://www.amazon.com/s/?field-titl...ltered=1&fap=1
Search Kindle for album by joanna slan: : Server response error (missing "h1 id=s-result-count")
Traceback (most recent call last):
File "calibre_plugins.overdrive_link.jobs", line 926, in find_book_at_lib
File "calibre_plugins.overdrive_link.amazon", line 428, in find_books
File "calibre_plugins.overdrive_link.parseweb", line 245, in must_find
LibraryError: u'missing "h1 id=s-result-count"'