I have recently been having issues in one of my Excel sheets, I have created a data validation drop down box that refers to a list in an adjacent column (unhidden).
Until today when I clicked on the cell, the drop down arrow appeared but now it briefly flashes before disappearing again, if you click on the right of the cell it still lets you make the selection but other people will use this sheet so it's not really acceptable.
I have checked that the data validation 'In-cell drop down' box is ticked and I don't know where to go from there, has anyone else had this problem? (Google has not been very helpful).
I had the same problem and found out that this issue was in my case only related to the speed of the Excel Sheet itself. I had various <strong>linked pictures</strong> in the workbook that made it very slow, resulting as well in the data validation arrow issue.
Removing the linked pictures would improve the performance and resolve the issue.
(Previously I could resolve it with a workaround by creating a macro in "ThisWorkbook" that goes on two sheets and selects the fields with data validation activated when the workbook is launched:
Strange enough, this was sufficient to solve the problem.)
I've never personally seen this but have you tried it on another computer or as another user on your computer? I think it just might be some temp files or cache from office that is causing this issue.