date formatting in excel online

I have been working in an online Excel spreadsheet for years. I had formatted the dates in the columns as: 3/12/24. Recently when I enter a date it autoformats to 3/12/2024. When I highlight the column to reset the dates, it no longer formats the column, so I have to go in and format each cell individually. Did something change that this is no longer a feature? How can I set the date format for an entire column? 

Thanks,

blware