while "Save to Disk", OPF document not opening in my computer

While executing "Save to Disk", OPF document not opening in my computer.

Request to help

Error as follows

calibre, version 3.23.0
ERROR: Could not open e-book: Failed to read book, D:\Z PERSONAL\UDEMY\DIGITAL BANKING COURSE\A STORY OF DIGITAL BANKING - CHAPTER 0\E-BOOK\TRIAL AND ERROR\Vaidyahripad\quick view of Global Digitking in Just 30 minutes, A\quick view of Global Digital Bankiust 30 minutes, A - Shripad Vaidya.opf click "Show Details" for more information

Traceback (most recent call last):
File "site-packages\calibre\utils\ipc\simple_worker.py", line 284, in main
File "site-packages\calibre\ebooks\oeb\iterator\book.py", line 65, in extract_book
File "site-packages\calibre\customize\conversion.py", line 245, in __call__
File "site-packages\calibre\ebooks\conversion\plugins\html_in put.py", line 87, in convert
File "site-packages\calibre\ebooks\conversion\plumber.py", line 1292, in create_oebbook
File "site-packages\calibre\ebooks\oeb\reader.py", line 72, in __call__
File "site-packages\calibre\ebooks\oeb\reader.py", line 703, in _all_from_opf
File "site-packages\calibre\ebooks\oeb\reader.py", line 348, in _spine_from_opf
OEBError: Spine is empty