£3000?? and they won’t demobstrate or schedule how to set up to customer needs! One things for sure, they wouldn’t be in business long in England or Wales.
Fogstar come configured with the Can Pylontech protocol, which should be ok for Sunsynk, but not sure what BMS you have on the new battery, I would have to look. Becareful, if in doubt by all means ask me but, fogstar is helpful providing instructions over the phone in real time, whils’t you do it.
It really is the the job of the installer during commisioning mate.