Postmaster.io fit packages error

gistfile1.sh

curl https://api.postmaster.io/v1/packages/fit \
    -u {{apikey}}: \
    -H "Content-Type: application/json" \
    -d '{
    "items":[
        {
            "width":5,
            "length":7,
            "height":10,
            "count":4,
            "dimension_units": "CM"
        }
    ],
    "packages":[
        {
            "width":6,
            "length":6,
            "height":6,
            "dimension_units": "CM"
        },
        {
            "width":12,
            "length":12,
            "height":12,
            "dimension_units": "CM"
        }
    ]
}'

{"message": "Transient error, please try again later.", "code": 500}