[PeterT]

Ok. Had another loan show up today. Onyx Storm. While yes, the Borrow button was available, clicking it resulted in

Spoiler:

calibre, version 8.6.0
ERROR: Unhandled exception: <b>ClientBadRequestError</b>: Failed to borrow book<p>This title is no longer available. You may be able to place it on hold, or add it to your wish list and borrow it later. [errorcode: TitleNoLongerAvailable]</p>

calibre 8.6  embedded-python: True
Linux-6.6.76-08024-gb30cb4a129c2-x86_64-with-glibc2.36 Linux ('64bit', 'ELF')
('Linux', '6.6.76-08024-gb30cb4a129c2', '#1 SMP PREEMPT_DYNAMIC Fri, 25 Apr 2025 05:08:33 -0700')
Python 3.11.12
Interface language: None
EXE path: /opt/calibre/bin/calibre-debug
Successfully initialized third party plugins: DeACSM (0, 0, 16) && LCPL Input (0, 0, 5) && DeDRM (10, 0, 9) && Annotations (1, 17, 13) && Backup Configuration Folder (1, 1, 2) && EpubMerge (3, 2, 0) && EpubSplit (3, 11, 0) && Find Duplicates (1, 10, 9) && Goodreads (1, 8, 3) && Kindle hi-res covers (0, 5, 1) && Kobo Metadata (1, 11, 0) && Kobo Utilities (2, 23, 0) && Manage Series (1, 5, 2) && OverDrive Libby (0, 2, 102) && Quality Check (1, 14, 2) && Reading List (1, 15, 6) && SmartEject (2, 6, 1) && View Manager (1, 10, 3)
Traceback (most recent call last):
  File "calibre_plugins.overdrive_libby.libby.client", line 522, in _send_request
    response = req_opener.open(req, timeout=self.timeout)
               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "urllib/request.py", line 525, in open
  File "urllib/request.py", line 634, in http_response
  File "urllib/request.py", line 563, in error
  File "urllib/request.py", line 496, in _call_chain
  File "urllib/request.py", line 643, in http_error_default
urllib.error.HTTPError: HTTP Error 400: Bad Request

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "calibre/gui2/threaded_jobs.py", line 85, in start_work
  File "calibre_plugins.overdrive_libby.borrow_book", line 40, in __call__
    loan = libby_client.borrow_media(media, card, is_lucky_day_loan)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "calibre_plugins.overdrive_libby.libby.client", line 950, in borrow_media
    return self.borrow_title(
           ^^^^^^^^^^^^^^^^^^
  File "calibre_plugins.overdrive_libby.libby.client", line 925, in borrow_title
    res: Dict = self.send_request(
                ^^^^^^^^^^^^^^^^^^
  File "calibre_plugins.overdrive_libby.libby.client", line 599, in send_request
    return self._send_request(*args, **kwargs)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "calibre_plugins.overdrive_libby.libby.client", line 542, in _send_request
    ErrorHandler.process(e, error_response)
  File "calibre_plugins.overdrive_libby.libby.errors", line 124, in process
    raise error_info["error"](
calibre_plugins.overdrive_libby.libby.errors.ClientBadRequestError: <calibre_plugins.overdrive_libby.libby.errors.ClientBadRequestError; http_status=400, msg='This title is no longer available. You may be able to place it on hold, or add it to your wish list and borrow it later. [errorcode: TitleNoLongerAvailable]', error_response='{"result":"upstream_failure","upstream":{"errorCode":"TitleNoLongerAvailable","service":"THUNDER","httpStatus":400,"userExplanation":"This title is no longer available. You may be able to place it on hold, or add it to your wish list and borrow it later.","correlationId":"ea9444c32103fdafd05589a9a5d26d9e"}}''>

|Admittedly this might have been a second click on the button; the first time had no error and no change to any status so I assumed the click had not registered.

Luckily I was in debug mode, so attached find the JSON from a search and the log.