Yeah, they used to sell an extended warranty, think it was about £120 for 10 years. Not sure if they still do it now though.
Question though, what is the model number? - As it might not be the inverter it could be the solar PV/generating side of things, as the fault codes aren't always the same for every model (annoyingly) so best to check thoroughly
Fronius IGTL3.0
Down side of this is I'd earmarked this years FIT payments to pay for more Lifepo4 batteries, money will now go on a new inverter Probably.
This vid shows the same issue.
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Fronius Inverter STATE 301 Error
Is your Fronius solar inverter displaying a STATE 301 error message on the screen? Find out what it means and what you can do about it here with Gold Coast S...
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On a positive note, My DIY setup worked without issue left running my house during a 2 week trip to Scotland.
Monitored via the Victron Venus OS on a Raspberry Pi via the Victron's VRM portal.(everything can be configured/shut down via the web)