SST showing just one side of the parallel slalom

Check your input mapping in the software and make sure that you have assigned the correct channels to the other course start and finish. One thing I have heard is that to see the mapping you must first change the connection to serial (I always use serial so I am not sure about this). For some reason the USB connection input mapping does not populate correctly.

Yes. Split Second is looking for only the default channel 0 for start and channel 1 for finish that normal single course operation uses.

Go into the serial settings for timers and alter the setting to "DUAL TIMY 9600" it is one of the choices at the bottom of the list.

That will set the default settings to

Channel 0 start - red/yellow
Channel 1 finish - red/yellow
Channel 3 start - blue/green
Channel 4 finish - blue/green

Split Second is working on this as we write.