Axpert Max II (Firmware 75.01) — MPPT stuck at 90V bug. Looking for update.

Hi everyone,

I am facing the notorious MPPT stuck bug on my Voltronic Axpert Max II inverter and am looking for a firmware update or a patched version to fix it.

My current system specifications:

• Inverter: Axpert Max II

• Main CPU Firmware: 75.01

• Secondary CPU (HMI) Firmware: 39.06

• PV Array: 11 panels in a single series string (Vmp is around 37V per panel, total Vmp under load is approx. 407V).

The Problem:

Even though my total string voltage under load should ideally sit around 400V, the MPPT tracker regularly drops down and gets stuck at exactly 90V (the absolute minimum PV threshold). When this happens, PV production drops to almost zero (10-50W).

A manual PV disconnect/reconnect via the circuit breaker forces a rescan and brings the voltage back to normal, but it gets stuck at 90V again as soon as there is a passing cloud or a shift in solar irradiance.

Could anyone please share a newer factory firmware or a stable patched firmware for the 75.XX series that resolves this MPPT scanning/freezing issue?

Any help, links, or advice would be greatly appreciated. Thank you!