[ext23]

All my books are just in the "Books" folder already...

Screenshots: https://imgur.com/a/GprpVWL

I changed it to "Documents," restarted Calibre, and got this error:

calibre, version 6.25.0
ERROR: Error: Error communicating with device

C:\r\src\src\calibre\devices\mtp\windows\content_enumeration.cpp:710:Cannot write to file:[hr=0x80004005 wCode=0] Unspecified error

Traceback (most recent call last):
  File "calibre\gui2\device.py", line 104, in run
  File "calibre\gui2\device.py", line 556, in _books
  File "calibre\devices\mtp\driver.py", line 224, in books
  File "calibre\devices\mtp\driver.py", line 197, in get_driveinfo
  File "calibre\devices\mtp\driver.py", line 187, in _update_drive_info
  File "calibre\devices\mtp\driver.py", line 157, in put_calibre_file
  File "calibre\devices\mtp\windows\driver.py", line 35, in check_thread
  File "calibre\devices\mtp\windows\driver.py", line 444, in put_file
wpd.WPDError: C:\r\src\src\calibre\devices\mtp\windows\content_enumeration.cpp:710:Cannot write to file:[hr=0x80004005 wCode=0] Unspecified error

It worked a few days ago, I haven't changed anything.