Hi,
Sorry it took me so long.
I am not sure where do I find the import/export settings?
Didn't see anything like this in the Settings of the plugin (apart of enabling the new products import).
I unset the setting "Use custom import format" and the import started working! (Actually, compared the settings with a different site using this plugin, which had the import working).
The import file had only the fields "id,sku,price,override_price".
So, my issue is resolved. Thanks.