Excel no longer saves comment

Hi Excel 365 for Mac has suddenly stopped saving "comments" It's fine until I reopen the spreadsheet and then they are gone! Any ideas?

Cheers

Try this in the spreadsheet:
File tab > Options > Advanced > Under Display, For cells with comments, show: Comments and indicators.

Alex

Alex tried that but it made no difference, but I did just notice the file has been changed to a .xlsb file. Saved it as .xls and all is back to normal.

Thanks Dave