Is it a repeating field? Sharepoint does not have the ability to display relational or repeating data and often we use a Database instead.
Checkboxes should have a value for both checked and unchecked but this often needs to be set in the controls if it is not a boolean (true / false) field. Once this value is set in your main data source you should be able to promote it. If it is repeating you should at least get the first value.
Maybe share more details if still needing help.