Data validation drop down list stopped working

[fijibound]

Been using data validation with a drop down list on a column in a worksheet for months with no issue.

Today I have noticed that there is no longer a drop down list on any of these cells, and instead all I can do is enter text manually.

I've check the data validation rule and it's still set to list, and have confirmed the source range is still correct. In-cell drop down option still ticked. No idea where else to look or why this has suddenly stopped working. Excel 2016 on Windows 10. Could anybody help please?

 

[Yongle]

Is the data entered still being correctly validated?
Try entering something invalid

 

[fijibound]

Hi Yongle. Thank you for your reply.

Just tried typing 'test' into one of these cells and it is indeed being validated; got popup telling me value doesn't match restrictions.

So it seems what is broken is that I don't have a drop down box to select the data from anymore.

 

[Yongle]

Sounds like the In-Cell Dropdown box is not checked
Click on Data Validation when in the cell with DV - the box to check is on the first screen