DataValidation showDropDown not working

[ana-stankovic]

I am using pandas and openpyxl to generate a excell sheet. Everything works except:

validation = DataValidation(
    type="list",
    formula1='"Keep,Delete,Production"',
    allow_blank=True,
    showDropDown=True
)

Validation to the cells is added, but the dropdown is not shown and it has to be added manually.