Anyone has any idea why I can't validate my data using List.
I tried to set it up both ways: cell reference, and comma split.

I worked with the same sheet yesterday, and I could validate the data using
List. But when I tried today with a different cell. The drop-down arrow sign
show up when that cell is selected, but the list didn't pop up.

I did not know how to disable this feature using any VB code, so there is
unlikely that there is any code modification...

Any idea? Really strange!!!!