I would think you should start with your installer, I'd wonder if they even wired up the Gateway properly for solar monitoring, it really should just take proper placement of the Current Transducers (CTs), but if they didn't do that for solar or did it wrong there likely won't be anything Tesla can do remotely to help. It could be that the installer did everything right and just didn't tell Tesla the right thing, sounds like you got your solar through someone else so Tesla may have only seen (or only been informed of) the Powerwall install.