Error when adding books to calibre

I had to re-install install calibre on my computer after my computer crashed and had to re-install Windows 10. The calibre library was preserved on an offsite NAS. However, since re-installing calibre on my computer, I keep getting an error message when I try to add a book to the library (and I can't even view books from the prior library.) Prior to the re-installation everything worked smoothly. I haven't changed any of the default calibre settings. I tried starting a fresh library and adding books from the old library, I get the same error code:

calibre, version 2.50.1
ERROR: Errors while adding: Failed to add any books, click "Show details" for more information


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Failed to add the book: Modern Buddhism 1: Sutra
//nas_romeo/Books/Geshe Kelsang Gyatso/Modern Buddhism 1_ Sutra (8)/Modern Buddhism 1_ Sutra - Geshe Kelsang Gyatso.epub
With error:
Traceback (most recent call last):
File "site-packages\calibre\gui2\add.py", line 369, in add_book
File "site-packages\calibre\db\legacy.py", line 214, in create_book_entry
File "site-packages\calibre\db\cache.py", line 57, in call_func_with_lock
File "site-packages\calibre\db\cache.py", line 1519, in create_book_entry
File "site-packages\calibre\db\cache.py", line 1248, in set_metadata
File "site-packages\calibre\db\cache.py", line 1075, in update_path
File "site-packages\calibre\db\backend.py", line 1530, in update_path
File "site-packages\calibre\db\tables.py", line 130, in set_path
File "site-packages\calibre\db\backend.py", line 808, in execute
File "c:\cygwin64\home\kovid\sw\build\apsw-3.8.2-r1\src\cursor.c", line 231, in resetcursor
CantOpenError: CantOpenError: unable to open database file