csv import error: must have exactly 20 columns

Question

I'm trying to import a csv file to a data table. I'm presented with a list of columns and able to select the searchable ones.

1. I Click continue
2. I get a dialog 'The file has more rows than allowed. Only the initial 5000 rows will be imported if you proceed'. I click 'Import Now'
3. An error message flashes in the bottom-right corner saying something like 'must have exactly 20 columns'
4. The program ends up hanging indefinitely.