Hi Guys. The exact same thing happened to me a week ago. Changed the communication cable but no luck. This is a 8kW Sunsynk with 2 x Dyness batteries. I got some advice from another inverter technician and he suggests I do a firmware update on the battery. I'm still asking around. In a way I'm glad it is not just me. My supplier where I bought the Batteries told me it is with Sunsynk. Did anyone do the factory reset on the inverter and did it work or did someone figured it out?