Multiplus completely down after failed firmware update

So I’m having a bit of a crisis…
My whole system has shut down - no AC or DC even when I’m plugged into shore power.
I have just transported my fifth-wheel trailer back home for the winter. My system was working fine until I got home.

The battery had discharged to 87 SOC so I isolated it from the inverter/charger, (as I disconnect it to store through the winter). This is the same as I did last year with no issue.
I plugged the trailer into our house 120v, plugged in the printer, and the whole system went down - no AC or DC
Since I first installed my system, I’ve had issues with a ‘low battery’ alarm when I print something on my Brother Printer, or first start up the system with the printer plugged in.
I connected my MK3 VE Bus to do an update, but it failed.
I read in a previous article that if the lights are all off and you cannot connect to any unit in the Victron App, the inverter is broken. My issue is that the company I purchased my system from has closed.
Who do I see about this?

These are my components
Victron 150/60 Smart Solar
Victron Multiplus II 2000 Inverter
BMV712 Smart Shunt
DMC 200/200A GX
HubLion 300Ah Battery

Have you tried ve.flash?

Thanks for the reply. What is VE Flash?

I just found ve.flash - I’ll look into it, but I can’t connect to the inverter through the app because it’s down.