parse error Document is empty, line 1, column 1 (<string>, line 1)

I'm trying to use FindingAPI but im getting this error on with PROD credentials. I think the problem is within the API

    try:
        api = Connection(config_file='ebay.dev.yml',  domain="api.ebay.com", debug=True, siteid='EBAY-US', escape_xml=False)
        request = {
            'keywords': "luka doncic",
            'itemFilter': [
                {'name': 'Condition', 'value': 'used'},
                {'name': 'SoldItemsOnly', 'value': 'true'}
            ],
            'paginationInput': {
                'entriesPerPage': 1,
                'pageNumber': 1
            },
            'sortOrder': 'PricePlusShippingLowest'
        }

        response = api.execute('findCompletedItems', request)
        print(response)

    except ConnectionError as e:
        print(e)
        print(e.response.dict())

timotheus / ebaysdk-python

parse error Document is empty, line 1, column 1 (<string>, line 1) #337