Describes the cause and action for error messages.
Error Message(English)：
cannot unprotect worksheet
The Unprotect option is not available to me. Why? How to Get it ...
https://www.mrexcel.com/forum/excel-questions/946087-unprotect-option-not-available-me-why-how-get-b・・・
How to protect worksheets and unprotect Excel sheet without password
https://www.ablebits.com/office-addins-blog/2016/02/10/protect-unprotect-excel-sheet-password/
Excel worksheet protection ...
https://www.ablebits.com/office-addins-blog/2016/02/10/protect-unprotect-excel-sheet-password/#excel・・・
How to unlock Excel ...
https://www.ablebits.com/office-addins-blog/2016/02/10/protect-unprotect-excel-sheet-password/#unloc・・・
How to protect a workbook ...
https://www.ablebits.com/office-addins-blog/2016/02/10/protect-unprotect-excel-sheet-password/#prote・・・
Protect a worksheet - Excel - Office Support - Office 365
https://support.office.com/en-us/article/protect-a-worksheet-3179efdb-1285-4d49-a9c3-f4ca36276de6
Top 3 Ways to Unprotect Excel 2016 without Password - PassFab
https://www.passfab.com/excel/how-to-unprotect-excel-2016-without-password.html
Can't unprotect an excel worksheet in Workbook_BeforeSave - Stack ...
https://stackoverflow.com/questions/14404567/cant-unprotect-an-excel-worksheet-in-workbook-beforesav・・・
How to Unprotect an excel sheet without password
https://uknowit.uwgb.edu/page.php?id=28850