Can't change name of sheet in Numbers

Hello: I'm trying to change the name of a sheet in my Numbers workbook and am unable to. I double click on the tab, enter the new name, and it looks good. Then when I hit enter, it reverts to the old name and I get that atrocious "boop" sound. Have also tried using the format option. Any suggestions? I'm using Catalina 10.15.7 on a MacBook Pro 13", 2020, four Thunderbolt 3 ports.

Thanks in advance,

Laura