spreadsheet index.xml file missing from existing password protected spreadsheet
iMac
What spreadsheet, Excel, ...? What computer model/year? What error message if any? Did you create the spreadsheet? Did you check with the spreadsheet developer for help, Microsoft for example?
The index.xml file is unique to iWork '09 applications including Numbers '09 v2.3. You will get an index.xml file missing from these vintage iWork applications when you attempt to open current Pages v5, Numbers v3, or Keynote v6 documents in the older applications. The new documents do not contain the index.xml file and are not backwards compatible. Solution: Quit Numbers '09. Double-click on the same document to open it in Numbers v3+, and provide the password.
One could improperly force a rename of an Excel (.xlsx) spreadsheet to .numbers, and attempt to open it in Numbers '09 — which would then also pop the message about the missing index.xml file.
spreadsheet index.xml file missing from existing password protected spreadsheet
