Can't see in-cell dropdown using data validation

I have a number of sheets in a workbook and am using some form of data validation in each of the worksheets. Some of the worksheets are not showing the in-cell dropdown even though I have this feature checked. Is there something that may be turned off in one of these worksheets that is not allowing me to see the in-cell dropdown? This is the first time I have seen this happen. Thanks for any comments.