I would disconnect the cables from the output of Quattro and check if the fault happens when you turn all on.
If it doesn’t, then you have an electrical fault down the line from the inverter causing it to short.
If its still happening, then you have a faulty Quattro.
At my house the cerbo got hit through the connection to the energy meter. And then a lot of the lan networked things connected to the cerbo got fried.
I have since isolated the lan network side from the solar stuff to prevent it happening in future… So even though the electrical side is properly isolated with surge arrestors, the lan network side can easily cause issues.
So I hope it didnt come in through your lan network and break something in your quattro.
Did you remove the cable from AC-out inside the inverter, and test the inverter completely disconnected? No blown surge arrestors?
Also unplug the VE.Bus cable going to the Cerbo.
If inverter fails to switch on with everything (except its DC supply) disconnected, then you have a damaged inverter.
Remember that even a long cable connected to the inverter can pick up a lightning strike, because the EMP generated by a nearby strike will induce a current (and therefore a voltage) in any conductor in the immediate vicinity. Of course, the job of the surge arrestor is to “short circuit” this surge and keep it below some save voltage, often blowing itself up in the process.