ConnectEasy can only support scales with a native USB interface.
Some scales, such as the Metler Toledo PS60, can use a 9-pin connector or something similar. Converters such as these are useful for emulating a serial port on computers which don't have one. However, ConnectEasy is unable to recognize scales connected to computers via anything other than a native USB.
If you are interested in the option of connecting a scale via a USB converter, please place a feature request.