Dash dataTable conditional cell formatting isn't working

I do not think you will need a callback for this like said in the tutorial. According to the last example of the tutorial I think you have a typo (one ' to much).

Change this line

'filter': 'col1' > num(15)' 

to:

'filter': 'col1 > num(15)'

I had the same issue and i found that giving the index directly rather than a condition was a lot easier.

style_data_conditional = [{'if': {'column_id': 'col1',"row_index": x},'backgroundColor': '#3D9970','color': 'white'} for x in df[df['col1']>15].index ]

it's ugly as it has been hard coded but it did the trick for me when the direct filter did not.