Using Win11 Home 23H2 and Office 365 local.

I have customized my Book.xltx and Sheet.xltx files with the font style and size I want for all new files, and that seems to work. But when I set a different color for the gridlines in these 2 files, opening a new blank workbook doesn't have the desired gridline color, or default text in cell A1. The gridlines are the default light grey and all cells are blank. I have stored copies of my customized Book and Sheet files in the 3 locations I've found referenced, but none of them work. One of these locations has my Personal.xlsb file in it, and that does get opened.

Where is Excel getting the template to use for the new blank worksheet? Here are the 3 locations where I have the copies of the Book and Sheet files:

• C:\Users\alanc\AppData\Roaming\Microsoft\Excel\XLS TART
• C:\Users\alanc\AppData\Roaming\Microsoft\Templates
• C:\Users\alanc\Documents\Custom Office Templates

This is driving me crazy; any help will be greatly appreciated.
Retired ChE

I also customized the gridline color in these 2 files, but new spreadsheets don't have my custom color either. Where in the world is the default spreadsheet getting its settings?