Kindle Fire giving "invalid MTP path" error

[Deadser]

Hi all! (My first post here!)

I've been looking around for a couple of days, but haven't seen anybody with this particular problem, and I've tried a couple of the solutions for similar problems with no luck.

I have a Fire with an SD card, and I have no trouble sending books from calibre to the SD card via USB cord or wirelessly. However, if I try to open one of the books on the SD card from within Calibre, I get a "[directory location] is not a valid MTP path" error. Now, normally, there would be no need to open the SD card copy of the book from within Calibre (I can read the books on the Kindle, and from my Calibre library), but for some reason, the newer books are showing up as a long string of alphanumeric numbers. (I think it might be the new .kfx format that causes that, right?) Anyway, I want to be able to open them this way so that I can figure out which book is which when looking at the device via Calibre.

I thought initially that it might have been because they were .kfx files, but some of them weren't, and I did download a few to the PC in .azw3 format. No luck. I've also tried:
1. different USB cords, including the original (at least I think it was). No luck. Besides which, I've had no trouble transferring, or deleting via any of the cords.

2. removing and reseating the SD card.

3. running a chkdsk on the SD card.

4. deleting a book from the device and reloading it.

5. clearing all scanned directories, restarting the Fire, and readding them.

6. removing MTP drivers and reinstalling them.

7. checked antivirus and firewall for Calibre permissions and disabled firewall (but not antivirus)

and I'm probably forgetting one or two others. Still no luck.

calibre, version 3.1.0
ERROR: Error: Error communicating with device

mtp:::%22oD9D5A%22:::Storage device/Android/data/com.amazon.kindle/files/Books/amzn1.account.AGDLJWLO66CARHNZGPLNRDTT673A/B00BATIK34/CR!0JGK5V96ZS2HZEDYG8VKHB00AN2C.kfx is not a valid MTP path

Traceback (most recent call last):
  File "site-packages\calibre\gui2\device.py", line 88, in run
  File "site-packages\calibre\gui2\device.py", line 642, in _view_book
  File "site-packages\calibre\devices\mtp\driver.py", line 328, in get_file
  File "site-packages\calibre\devices\mtp\filesystem_cache.py", line 248, in resolve_mtp_id_path
ValueError: mtp:::%22oD9D5A%22:::Storage device/Android/data/com.amazon.kindle/files/Books/amzn1.account.AGDLJWLO66CARHNZGPLNRDTT673A/B00BATIK34/CR!0JGK5V96ZS2HZEDYG8VKHB00AN2C.kfx is not a valid MTP path

Any ideas? It used to work just fine, so I'm thinking maybe an update to Calibre or the Fire itself?

[kovidgoyal]

There have not been any changes to MTP support in calibre in a very long time. The actual error you posted is for a FKX file which cannot be viewed/downloaded in any case. Do you get the exact same error for azw3 or mobi files?

[Deadser]

I think so. I haven't been able to open anything, no matter the format.

calibre, version 3.1.0
ERROR: Error: Error communicating with device

mtp:::%22oE04AC%22:::Storage device/Books/Hormone Diet, The - Natasha Turner ND.mobi is not a valid MTP path

Traceback (most recent call last):
  File "site-packages\calibre\gui2\device.py", line 88, in run
  File "site-packages\calibre\gui2\device.py", line 642, in _view_book
  File "site-packages\calibre\devices\mtp\driver.py", line 328, in get_file
  File "site-packages\calibre\devices\mtp\filesystem_cache.py", line 248, in resolve_mtp_id_path
ValueError: mtp:::%22oE04AC%22:::Storage device/Books/Hormone Diet, The - Natasha Turner ND.mobi is not a valid MTP path

and here's an azw3:

calibre, version 3.1.0
ERROR: Error: Error communicating with device

mtp:::%22oD97BB%22:::Storage device/Books/Cipher, The - Kathe Koja.azw3 is not a valid MTP path

Traceback (most recent call last):
  File "site-packages\calibre\gui2\device.py", line 88, in run
  File "site-packages\calibre\gui2\device.py", line 642, in _view_book
  File "site-packages\calibre\devices\mtp\driver.py", line 328, in get_file
  File "site-packages\calibre\devices\mtp\filesystem_cache.py", line 248, in resolve_mtp_id_path
ValueError: mtp:::%22oD97BB%22:::Storage device/Books/Cipher, The - Kathe Koja.azw3 is not a valid MTP path