Describes the cause and action for error messages.
Error Message(English)：
subtotal does not group
Insert subtotals in a list of data in a worksheet - Excel - Office Support
https://support.office.com/en-ie/article/insert-subtotals-in-a-list-of-data-in-a-worksheet-7881d256-・・・
Excel 2016: Groups and Subtotals - GCFLearnFree - GCFGlobal
https://edu.gcfglobal.org/en/excel2016/groups-and-subtotals/1/
Excel 2016- Groups & Subtotals - YouTube
https://www.youtube.com/watch?v=ISWhssnx3BY
https://www.youtube.com/watch?v=ISWhssnx3BY
Excel 2013: Groups and Subtotals - YouTube
https://www.youtube.com/watch?v=oFdhANcS6VA
https://www.youtube.com/watch?v=oFdhANcS6VA
Excel: Group rows automatically or manually, collapse and expand rows
https://www.ablebits.com/office-addins-blog/2017/12/28/excel-group-rows/
Subtotals in Excel: how to insert, use and remove - Ablebits.com
https://www.ablebits.com/office-addins-blog/2016/08/11/subtotal-excel-insert-use-remove/
Excel Tip of the Week #62 - Group, ungroup, subtotal - Blogs - IT ...
https://ion.icaew.com/itcounts/b/weblog/posts/exceltipoftheweek62groupungroupsubtotal