getting <InternalFailure/>

[nikhilsquareboat]

I am trying to access AWS rekognition service

var instanceXML = AWS.request('rekognition', 'us-east-1','RekognitionService.ListCollections',null, "POST");

getting

when I am hitting with post man I am getting proper data which is show below
{
"CollectionIds": [
"collection1",
"collection2"
],
"FaceModelVersions": [
"4.0",
"4.0"
]
}