JIRA Search API request Not returning data for all Fields

[Aram Watson]

I need to request all the issues from a project and every field an issue has as well as the data in each field.

The server I'm pulling from uses some custom fields that don't return data when I make the API search request. It will show me the name of the ID of the custom fields but No data will be there.

Would be very helpful if anyone had some insight into why some custom fields return data and other don't.