Anyone know how to fix this calibre error?

[NoGoingBack]

Hi I added pictures to my ebook, and now I get this error opening it
any help would be appreciated

calibre, version 6.7.1
ERROR: Loading book failed: Failed to open the book at C:\Users\Owner\Desktop\Story Line No Going Back - Unknown.opf. Click "Show details" for more info.

Failed to convert book: C:\Users\Owner\Desktop\Story Line No Going Back - Unknown.opf with error:
InputFormatPlugin: HTML Input running
on C:\Users\Owner\Desktop\Story Line No Going Back - Unknown.opf
Parsing all content...
Failed to run pipe worker with command: from calibre.srv.render_book import viewer_main; viewer_main()
Traceback (most recent call last):
  File "runpy.py", line 196, in _run_module_as_main
  File "runpy.py", line 86, in _run_code
  File "site.py", line 82, in <module>
  File "site.py", line 77, in main
  File "site.py", line 49, in run_entry_point
  File "calibre\utils\ipc\worker.py", line 196, in main
  File "<string>", line 1, in <module>
  File "calibre\srv\render_book.py", line 821, in viewer_main
  File "calibre\srv\render_book.py", line 812, in render_for_viewer
  File "calibre\srv\render_book.py", line 789, in render
  File "calibre\ebooks\oeb\iterator\book.py", line 62, in extract_book
  File "calibre\customize\conversion.py", line 242, in __call__
  File "calibre\ebooks\conversion\plugins\html_input.py", line 94, in convert
  File "calibre\ebooks\conversion\plumber.py", line 1323, in create_oebbook
  File "calibre\ebooks\oeb\reader.py", line 71, in __call__
  File "calibre\ebooks\oeb\reader.py", line 698, in _all_from_opf
  File "calibre\ebooks\oeb\reader.py", line 343, in _spine_from_opf
calibre.ebooks.oeb.base.OEBError: Spine is empty

[NoGoingBack]

Solved: I converted the book and the conversation fixed the new version. So now I can open it. thanks for allowing me to post