Currently the method **EntsoeRawClient.query_activated_balancing_energy_prices(**) includes the following properties among others: > if standard_market_product: params.update({'standardMarketProduct': standard_market_product}) if original_market_product: params.update({'originalMarketProduct': original_market_product}) response = self._base_request(params=params, start=start, end=end) The standardMarketProduct and originalMarketProduct are wrongly defined, shuld be: - standardMarketProduct -> **Standard_MarketProduct** - originalMarketProduct -> **Original_MarketProduct** This means the upper code snippet should look like: > if standard_market_product: params.update({'Standard_MarketProduct': standard_market_product}) if original_market_product: params.update({'Original_MarketProduct': original_market_product}) response = self._base_request(params=params, start=start, end=end) This is defined in the Swagger documentation. I kindly ask for your support.