Mac Excel 365 Changed the character used to separate thousands and decimals after office update

1. Modify the number formatting in Excel 
Select the affected cells → Right-click and select “Set Cell Format” (or Cmd + 1).
In the “Numbers” tab: 
select ‘Numeric’ or “Currency” format.
In the options on the right, manually specify: 
Decimal sign: . (period) 
Thousand separator: , (comma) 
Click OK to apply the changes.
2. Adjust system locale settings 
Open Mac System Settings → “Language & Locale”.
Check the following settings: 
Preferred Language: Make sure it is English (or another language that uses , as the thousands separator).
Region: Select USA, UK, etc. (avoid European countries such as Germany, France as they use the 1.000,00 format by default).
Restart Excel. 
3. Modify Excel default options 
In Excel, go to Excel > Preferences > Edit.
Find the Use system separator option: 
Uncheck this option.
Enter manually: 
Decimal separator: .
Thousand separators: . 
Restart Excel. 
4. Check the Office Language Pack 
Open Word or Excel → Click on Tools > Language in the menu bar.
Make sure the default editing language is English (US).
If a language pack is missing, go to the Microsoft 365 installer to download it.
5. Rebuild the Excel configuration file 
If the problem persists, the preferences file may be corrupted: 
Close Excel. 
Open Access → Press Cmd + Shift + G and enter the path: 
~/Library/Containers/com.microsoft.Excel/Data/Library/Preferences/ Delete the following files: com.microsoft.
Delete the following files: 
com.microsoft.Excel.plist 
all com.microsoft.Excel.XXXXXXX files.
Reopen Excel (the system automatically rebuilds the configuration file).