Hi,
Are you using SP 2013 or later? – if so, you must use a filter like this:
{"filterField":"YOUR_FIELD_NAME","filterValue":true,"operator":"eq"}
If you use SP 2010 or earlier you must use a filter like this:
"<Where><Eq><FieldRef Name='YOUR_FIELD_NAME' /><Value Type='Boolean'>1</Value></Eq></Where>"
Change YOUR_FIELD_NAME with your field name.
Alexander