Have you tried closing JMP and then reopening it?
If that does not work, take a look at what JMP produces as a script that can be used to create the given column. It will show you what Column Properties it has.
Run this little script and then look in the JMP log to see what column properties are listed.
// Replace the column name "height" with your column of interest
Show( :height << get script )
If this does not provide you with a solution, please attach a copy of your data table so the Community can look further into the issue.
Jim