I have an excel spreadsheet that is essentially an address list. It has 14 columns and about 400 rows. It has a header row with names like FNAME, LNAME, ADDRESS1, etc.
Now when I try to sort it even with the my data has headers checked the header row is treated as data. Also the sort criteria used to use the header values. Now it says Column A or (Column A). Every thing is data and the headers are centered.

This data was saved as xls. This year I added a 4th sort level and was warned of an incompatibility. I then saved it as an xlsx.

My office is Microsoft 365 and the Excel is version 2210.

Any suggestions for fixing this.