sergeyshadow

That's not a control board, that's the removable display board. In what way has it stopped working: just no activity on the display? No LEDs?
Presumably the inverter itself still works; the output on/off switch doesn't need power.
There are about 3 SMD fuses under the PCB. It's possible that these have failed; sometimes that's all that is wrong, but usually not.
There isn't a lot that goes wrong with the displays, so there are few posts on them. I have one here that mentions the fuses:
You should be able to buy a replacement complete display from whoever sold you the inverter, and occasionally from other sources. Beware that there is firmware inside the displays, and you need a model specific to your inverter model group. There are a few groups, e.g. Axpert King and Axpert VM III are in the same group, so they have the same firmware and you can use the same display on either inverter model. They all look the same, but because of the difference in firmware, you have to get one from the right group. My understanding is that you can't reflash say Axpert King display firmware into a removable display for an Axpert Max, although I've never tried, and with advanced gear like a JTAG programmer for ARM processors, you probably could.
The small cable from the display to the inverter is standard (straight through), you could try an ethernet cable to see if that cable happens to be the problem. The signals on that cable are not ethernet, it's just that any straight-through RJ-45 cable will work.

You are correct in that your MAX can't do what you want, which is called double conversion. Voltronic do make two models that do this; the Axpert King 1 and the Axpert King II. Since your panels are wired for high voltage, you could replace your MAX with two Axpert King IIs in parallel. It will convert incoming unstable AC power to DC (the ~400 VDC bus, not the 48 V battery), then convert it again to a stable 230 VAC (or 220 V or 240 V if you want). You lose a little efficiency with the double conversion, that's why most models don't have this feature. I believe that the Kings are designed for this scenario (poor utility voltage), though there is also the advantage of zero transfer time, for loads like auto teller machines that mustn't have interrupted power, even for 10 or 20 milliseconds.