There are a few possibilities:
1) Please check the date range is correct or not. If that is no request made during that date range filtered, the relevant report wouldn't be generated.
2) Please make sure the custom form visibility was turned on. The custom form's CSV report wouldn't be generated if the form was hidden.
3) You have deleted the custom form. So, before deleting the form, please make sure that you have exported the related custom form's CSV report from EasyWork Hub.