My neighbor has had a solar city system that was installed a few years ago. Even with my gateway hard wired into my router just weird I'm still having issues. Gateway is in same place it has always been
I was virtually certain that this was the case, actually. I have good news and bad news for you as I dealt with this exact scenario.
I will give you the TL ; DR version first, and then attempt to explain a bit further later.
TL ; DR... The only thing you can do is power cycle your inverter and "hope" your inverter connects back to your solar gateway. There is nothing else you can do to make this device connect. It is not your fault it is not connecting. Your inverter is connected to your neighbors solar gateway.
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Slightly longer explanation, as explained to me by tesla when I had this exact thing happen. I preface this with I am not a network technician, but am in IT and familiar with networking in general etc.
The solar gateway provides a connection to the inverter as we know, to report back to tesla solar generation. The way the inverters are configured (especially older ones before this past year or so) is that the inverter will simply connect to "the closest" tesla gateway it can find. when you took your solar gateway down, your inverter simply re connected to your neighbors solar gateway.
The inverters also tend to try to stay connected to "the last" gateway they connected to, so now, even though you have your new solar gateway plugged in, your inverter is still connecting to your neighbors tesla solar gateway. The only thing that is going over that connection (per tesla ) is solar generation data.
One thing you can do is call tesla and make sure they have assigned your new gateway to your account. Even with that done, it does not guarantee that your inverter will connect to YOUR solar gateway. Power cycling it may work or may not and there isnt much you or tesla can do especially if your neighbor still has the solar city "little white box" gateway which puts out a stronger signal than these newer little black box ones.