I found a cable that came with one of my inverters/batteries, but I think it was for my EG4, not the Sol-Ark or Pytes.
It is a USB-232 RJ45.
Looks like it might be worth a try.
disconnected SolarAssistant from the inverter in the settings.
Connected up to an available USB port on my SolarAssistant to the 'Console' port on the master battery. It did see the cable, so I changed from using 'Inverter settings' to 'USB PylonTech/Pytes' and saved.
Wasn't able to connect.
I then tried using the 'USB Serial RS232/485' instead
Maybe it doesn't want the CAN cable connected to the inverter at the same time, so removed that and tried again. still not happy. I changed the settings back to the original and connected as they were before.
I'm going to see if I can find a USB cable, cut off the end. Wire and crimp it up to match the diagram from Pytes and try again, but I'm thinking that the FTDI chip is important in this connection.
good luck. share what you figure out too.